The Ball Beneath the Game
A Century of Construction, Chemistry, and Consequence - How the Official Major League Baseball Has
Shaped the Sport from the Dead Ball Era to the Modern Humidor Age
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Abstract
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The official baseball — a sphere of cork, rubber, wool, and leather totaling just over five ounces — has never been static. Over the past century-plus, subtle and not-so-subtle alterations to its core composition, yarn winding tension, cover material, and seam geometry have repeatedly recalibrated the fundamental balance of offense and pitching. This study traces those changes from the anarchic, pitcher-dominated Dead Ball Era of the early twentieth century through the cushioned cork revolution of 1910 and 1925, the seam height controversies of the 1930s, the wartime deprivations of 1943–1945, the horsehide-to-cowhide transition of 1974, and into the aerodynamic mysteries of the twenty-first century’s home run surges and deliberate deadening. The article argues that no piece of equipment in professional sport carries more hidden consequence than the baseball itself, and that understanding its physical and chemical evolution is essential to any serious understanding of the game — its statistics, its strategies, and its enduring tensions.
This is the first study completed by the North Texas Sports Blog.
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SECTION 1
PREFACE -- "WHAT THE BALL REMEMBERS"
There is a room in the lower level of the National Baseball Hall of Fame in Cooperstown, New York, that most visitors will never see. It is not particularly dramatic. The lighting is controlled, the temperature regulated, and the air smells faintly of old leather and the particular dustiness that all important things eventually acquire. In this room, behind archival glass and within acid-free boxes, live dozens of baseballs from across the game’s history. To the untrained eye, they are identical. White spheres. Red Stitching. The same satisfying weight in the palm. A tourist passing through the lobby gift shop would be hard pressed to distinguish a 1907 ball from one used in last Tuesday night's game in Houston. And, upon the completion of gathering my research to complete this study, I have come to believe, this is one of the greatest optical illusions in the history of American sport.
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Because they are not the same ball. Not even close.
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Curators at the Hall of Fame describe a ball from 1907 as soft--soft in the way of a thing that has been used past its design tolerance, stained brown with decades of grime and the hands of men long dead. The ball from 1922--firmer, whiter, almost aggressively round, as though it had spent a century insisting on itself. The 1974 ball feels subtly different--the cover slightly rougher, the texture of a different animal's hide. The 2019 ball--Slick. Disturbingly slick. Like someone had shaved it.
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As the founder and editor of NTSB, my aim is, broadly construed, to learn the game well enough to write about it with the authority of experience and the humility of a lifelong student. The curious thing about conducting my research on this article is I have been led to an increasingly firm conviction: that every statistical era in baseball's history has been, in measurable part, a story about what was inside--and on the outside of--the ball. This is the premise of this study. Knowing in greater detail about the differences in baseballs used in the game during the course of the past century has led me to some interesting conclusions. And, in all honesty, I'm not all that surprised by the evidence.
A CENTURY OF BASEBALL CHANGES - KEY DATES
1910 — Cork-centered ball introduced by the Reach Company; adopted first by the American League.
1920 — Spitball and doctored pitches banned; umpires ordered to replace dirty balls; upgraded Australian wool yarn introduced. The Live Ball Era begins.
1925 — Milton Reach patents the “cushioned cork” center — layered cork, black rubber, and red rubber — the basis of the modern pill.
1931 — National League adopts raised-seam ball with five-strand cover; American League retains lower-seam “rabbit ball.” The two leagues play with different baseballs for seven years.
1943 — Wartime rubber shortage forces adoption of the balata ball. Nine of eleven Opening Day games are shutouts.
1961 — AL expansion to ten teams; pitching talent diluted; offense surges momentarily before conditions shift toward pitching dominance.
1974 — Horsehide cover officially replaced by cowhide on April 4, 1974 — the same day Hank Aaron ties Babe Ruth’s career home run record.
1977 — Rawlings wins exclusive MLB manufacturing contract, ending Spalding’s century-long dominance.
2000 — MLB ball production consolidated entirely in Rawlings’ Costa Rica facility, introducing computer-monitored winding tension calibration.
2015 — Home run rates begin a dramatic, unexplained multi-year climb. The aerodynamic era of controversy begins.
2021 — MLB deliberately loosens first winding tension; expands humidor use to ten ballparks. The Great Deadening.
SECTION II
THE ANARCHIC SPHERE - THE DEAD BALL ERA (1900-1919)
Imagine, if you will, playing the ninth inning of a July doubleheader in St. Louis with a ball that began its life in the first inning of the first game. It is no longer white. It has been spat upon, rubbed with mud, scuffed with emery boards hidden in belt buckles, and struck so many times that it has developed a subtle but material asymmetry. It is heavier on one side. It wobbles slightly as it rotates through the air. And in the failing light of a pre-twilight stadium with no artificial illumination, it is very nearly impossible to see.
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The standard baseball before 1910 used a rubber core — soft, low-resilience, and prone to losing what limited energy it possessed after repeated impacts. Balls were used for entire games, sometimes extended over dozens of innings, and they were replaced only when they became so obviously degraded that umpires could no longer in good conscience leave them in play. By that point, of course, they had been in play for far too long. They were misshapen, soft, brown, and aerodynamically compromised in ways that no one was measuring but every pitcher was exploiting.
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And legally. Let me emphasize that word. The spitball, the emery ball, the shine ball, the mud ball — all were legal and widely practiced. Pitchers like Ed Walsh of the White Sox, who won 40 games in 1908, built careers on the spitball. Russ Ford of the Highlanders secretly scuffed balls with a hidden emery ring to produce a pitch of almost supernatural movement. The ball was a co-conspirator.
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Strategy adapted with impressive ingenuity to these conditions. Small ball — contact, speed, and positioning — dominated because the ball simply did not carry. The stolen base was a genuine offensive weapon. The hit-and-run, the Baltimore chop, the sacrifice bunt, the squeeze play — these were not novelties. They were necessities imposed by physics. Ty Cobb, whose .366 career batting average remains the highest in professional baseball history, was a master precisely because he understood these constraints. He did not try to drive the ball. He placed it, sharpened his spikes, and ran. League home run leaders routinely hit fewer than ten home runs per season. The concept of the home run as a primary offensive weapon was, in the Dead Ball Era, genuinely foreign.
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This era in baseball history is unique. Players were routinely batting against balls they could not see in the late innings. The wonder is not that batting averages were low. The wonder is that anyone hit at all.
SECTION III
THE CORK REVOLUTION - 1910 AND THE FIRST LIVE BALL
The Reach Company’s introduction of the cork-centered baseball in 1910 — adopted first by the American League, then universally — was the first serious attempt to rethink what the ball actually was. The cork core replaced the old rubber core. It was livelier, more resilient, and crucially, it held its shape under repeated impact far better than its predecessor. When new, it was a distinctly better ball.
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The results were immediate and startling. The American League’s collective batting average jumped from .243 in 1910 to .273 in 1911 — a single-season shift of thirty points that had no equivalent precedent. Home runs increased. Scoring increased. Pitchers, who had enjoyed an era of near-total dominance, panicked.
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And so they adapted. The spitball proliferated. The emery ball, the shine ball, and every other form of doctored-pitch chicanery intensified — because pitchers needed new weapons to neutralize the livelier sphere. In a cruel irony that I find rather wonderful, the cork ball that was meant to enliven offense inadvertently triggered the most intensive pitching manipulation arms race in baseball history. The pitchers found ways to fight back. The doctored-pitch ecosystem grew elaborate.
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Furthermore, the cork ball’s advantage was conditional. It was livelier only when it was new and clean. Once it had been on the field for an inning or three — once it had been spat on, scuffed, muddied, and generally abused — its superiority over the old rubber core was largely negated. The structural constraints of the era reasserted themselves. The cork revolution, in 1910, was real but partial. The full revolution was still a decade away.
SECTION IV
THE GREAT DISRUPTION - 1920 AND THE LIVE BALL ERA
History rarely turns on a single event. The transformation of baseball in 1920 is sometimes narrated as the story of Babe Ruth and his supernatural capacity to hit the ball very far. This narrative is emotionally satisfying and not entirely wrong. But it is incomplete in ways that matter enormously to anyone who wants to understand what actually happened.
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The transition from the Dead Ball Era to the Live Ball Era was not caused by one change. It was a perfect and largely accidental storm of simultaneous developments, each of which would have been insufficient alone but which combined to produce one of the most dramatic sport-wide statistical revolutions ever recorded.
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First: the spitball and all its chemical cousins were banned before the 1920 season. Seventeen pitchers who had built careers on the spitball were grandfathered and permitted to continue using it for the remainder of their professional lives — a concession that strikes me as both generous and pragmatic — but no new practitioners were permitted. The emery ball, the shine ball, and all other doctored-pitch variations were also banned outright. An entire offensive handicap was removed overnight.
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Second: umpires were now explicitly instructed to replace dirty, discolored, or damaged balls with fresh ones throughout the game, rather than waiting until the ball was genuinely unusable. This instruction was partly accelerated by the death of Ray Chapman of the Cleveland Indians in August 1920, struck by a pitch he almost certainly could not see. Chapman’s death was the game’s first and only on-field fatality from a pitched ball, and it provided the moral urgency that MLB needed to enforce what had been, until then, a loosely observed recommendation.
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Third: the ball itself changed. Manufacturers upgraded to higher-grade Australian wool yarn and, critically, switched from hand winding to machine winding. Machine winding produced a tighter, more consistent sphere — more uniformly round, more evenly tensioned, with less variation between one ball and the next. The new balls were firmer, more resilient, and more predictable.
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Was the ball “juiced” in 1920? This is perhaps the oldest argument in baseball historiography. The U.S. Bureau of Standards tested the ball and found no significant measurable difference in its specifications. My view, arrived at after considerable study, is that the Bureau was asking the wrong question. The ball didn’t need to be chemically or mechanically altered to feel like a rocket ship compared to its predecessor. Clean balls, consistently replaced, with no doctoring permitted, wound more tightly and consistently — these factors were more than sufficient. The cumulative effect was overwhelming. By 1925, league home run rates had more than quadrupled compared to 1910.
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The 1922 ball was markedly different. It was firmer than the 1907 ball. It was noticeably whiter. It was, in its modest way, a more perfect object. And it changed everything.
SECTION V
THE CUSHIONED CORK CENTER AND THE HITTER'S PARADISE (1925-1930)
In 1925, Milton Reach patented what he called the “cushion cork” center: a sphere of cork surrounded first by a layer of black rubber, then by a layer of red rubber, creating a layered, shock-absorbing core that I can only describe as engineered serenity. This cushioned cork pill was more consistent, more resilient, and more forgiving of the small variations that inevitably occur in mass manufacturing. It is, in its essential structure, the basis of the baseball pill used today.
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Its effects on offense were not subtle. By 1930, the National League’s collective batting average reached .303 — the highest ever recorded for a full major league season. Hack Wilson hit 56 home runs and drove in an astonishing 191 runs that year, records that stood for decades. Babe Ruth and Lou Gehrig were producing numbers that read less like baseball statistics than like typos. Pitchers had almost no legal tools with which to fight back: the doctored-pitch arsenal was banned, the mound was at a fixed height, and the ball was an adversary of unprecedented liveliness.
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The era’s peak was glorious and unsustainable. Scoring was almost comically high. The game had overcorrected. The pendulum, as it always does in baseball, had swung so far in one direction that it had begun to undermine the competitive tension that makes the sport worth watching. It would take the events of the 1930s to begin pulling it back.
SECTION VI
THE SEAM WARS OF THE 1930S - WHEN THE TWO LEAGUES DISAGREED
One of the stranger episodes in baseball’s material history is one that has been almost entirely forgotten by the general public: for the better part of a decade in the 1930s, the National League and the American League played with meaningfully different baseballs. Not different in name or in specification on paper, but different in practice — different in seam height, in cover thickness, and in their aerodynamic consequences.
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In 1931, the National League adopted a ball with raised seams — five strands of thread instead of four, with a slightly thicker cover — with the explicit intention of helping pitchers grip the ball and moderating the offensive explosion that had produced the historical aberration of the 1930 season. The American League, home of Babe Ruth and the Yankees dynasty and thoroughly uninterested in moderating offense, retained its lower-seam ball.
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NL President Ford Frick, navigating this controversy in 1937, offered the classic diplomatic formulation: “The new ball will give the pitchers a better grip, but it will not impair the possibility of long hits if the ball is hit right.” This is the kind of statement that means almost everything and almost nothing simultaneously.
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In December 1937, the NL voted to further raise the seams of its ball while the AL retained its configuration. By 1938, the U.S. Bureau of Standards — called in to adjudicate, as it occasionally was when baseball needed scientific cover for decisions it had already effectively made — reported equivocally that “some are lively and some are less lively.” After 1938, both leagues agreed to conform to a single specification, and the great seam schism ended.
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The difference in seam height is not merely cosmetic. It is aerodynamic destiny. A higher seam catches more air. It creates more turbulence. The ball decelerates faster and does not carry as far. A lower seam does the opposite. The difference between the NL and AL balls of the 1930s was, in modern measurement terms, probably a matter of a few thousandths of an inch in seam height. And yet it produced meaningfully different games in the two leagues. History does not forgive us for not looking more closely.
SECTION VII
WARTIME AND MATERIALS SCARCITY - THE 1943-45 "BALATA BALL"
The Second World War imposed privations on nearly every American industry, and baseball was not exempt. By 1943, the rubber and cork needed to manufacture the cushioned cork pill were classified as strategic war materials, and MLB was compelled to substitute. The replacement was balata — a natural rubber substitute derived from the latex of tropical balata trees, previously used in the manufacture of golf ball covers and electrical insulation — wound around a compressed granulated cork core in place of the familiar layered rubber shells.
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The balata ball was dead. That is not a figure of speech. It was historically, measurably, almost insultingly dead. It had essentially no resilience. When struck, it absorbed energy rather than returning it. It was the physical opposite of the cushioned cork pill that had powered two decades of offense.
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On Opening Day of the 1943 season, nine of eleven games were shutouts. Nine. Of eleven. This statistic is both devastating and darkly comic — a perfect controlled experiment, unintentional and unrepeatable, demonstrating what happens to a professional baseball game when the ball is stripped of its capacity to respond. MLB quietly abandoned the balata ball mid-season and returned to a composite rubber/cork core using recovered and recycled materials. The experiment lasted barely a month at full implementation, but its lesson is permanent.
SECTION VIII
THE HORSEHIDE DECADES - STABILITY AND CREEPING ADVANTAGE
The post-war period brought, for a time, something baseball had rarely enjoyed: genuine stability in ball construction. The horsehide cover, which had been standard since the sport’s nineteenth-century origins, remained in use, prized for its thinness, relative smoothness, and the way it aged gracefully on the seams. It gripped the thread tightly and held its shape well across a range of temperature and humidity conditions. Four layers of wool yarn — gray 4-ply, white 3-ply, gray 3-ply, and a poly/cotton finishing layer that was gradually introduced across this era — remained the winding standard. The ball was fully standardized at 9 to 9.25 inches in circumference, 5 to 5.25 ounces, with a cushioned cork pill. Rawlings and Spalding produced the two leagues’ balls respectively, and the variation between them was, in this period, relatively modest.
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The 1950's was the golden standard of competitive balance — pitchers and hitters in rough equilibrium, the ball consistent enough that performance could be fairly attributed to performance. The integration of Black players into the major leagues beginning in 1947, and the widening talent pool it represented, produced a generation of athletes whose abilities tested the game’s constructs in genuinely new ways. Willie Mays, Henry Aaron, Ernie Banks — these men were operating within a material environment that was, for the first time in decades, not working systematically against them.
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But conditions quietly shifted through the late 1950s and into the early 1960s. The strike zone was expanded in 1963, returning approximately to its original pre-1950 dimensions. Parks grew larger. Pitching coaching became more sophisticated and specialized. The ball itself had not changed — but its aerodynamic interaction with a landscape that was gradually tilting toward pitching dominance would soon produce consequences that no one had fully anticipated.
SECTION IX
THE YEAR OF THE PITCHER - 1968 AND THE MOUND'S RESPONSE
1968 was, statistically, the most extraordinary season of pitching dominance in the live-ball era, and it arrived not because the ball changed but because everything around it had. Bob Gibson of the Cardinals posted an ERA of 1.12 — a figure so incredible that it reads less like a statistic than like a misprint. Denny McLain of the Tigers won 31 games. Carl Yastrzemski led the American League in batting with an average of .301 — the lowest average ever to win a batting title, in either league, in the history of the sport. The combined MLB batting average was .237. Shutouts were epidemic.
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The ball was the same ball that had been in use for years. But it was operating within a system that had stacked conditions against the hitter in ways that compounded each other: a mound permitted to reach 15 inches in height — giving pitchers a significant downhill angle that added both velocity and movement — an expanded strike zone that had been in effect for five seasons, and parks whose dimensions had grown as new facilities were built with an aesthetic preference for space over intimacy.
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MLB’s response for the 1969 season was decisive: lower the mound from 15 inches to 10 inches, where it has remained ever since, and shrink the strike zone back to its pre-1963 dimensions. The ball did not change. The offense returned. Batting averages climbed back toward .250 within a season. The lesson was, or should have been, clear. I put it plainly in Monograph No. 12 and I repeat it here: “The mound came down five inches. The ball didn’t change. The offense returned. The lesson was clear: the ball is not the only variable. It operates within a system.” The system includes the mound, the strike zone, the parks, the players, and the training regimes. The ball is the heart of that system — but it is not the whole body.
SECTION X
FROM HORSEHIDE TO COWHIDE - THE 1974 TRANSITION
By the early 1970s, horsehide was becoming genuinely scarce. Horses were increasingly valued for purposes other than the incidental yield of their hides, and the supply of high-quality horsehide adequate for baseball cover production — thin, consistent, appropriately pliable — was dwindling to a point where manufacturers were reporting meaningful supply constraints. The decision to switch to cowhide was not romantic. It was logistical.
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MLB approved the change, and the cowhide baseball made its official debut on April 4, 1974 — the same day Henry Aaron stepped to the plate at Cincinnati’s Riverfront Stadium and hit career home run number 714 to tie Babe Ruth. The coincidence was almost too neat for history: the last record of the horsehide era, tied on the first day of the cowhide era. The first balls were commemorated — Spalding NL balls and Reach AL balls stamped “Cowhide Baseball First Use 4-4-74” in small type beneath the commissioner’s signature.
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Cowhide is naturally thicker and more textured than horsehide, requiring more intensive shaving at the tannery to reach the required thickness for a baseball cover. The result, in the early transition, was a cover that many players described as subtly slicker — less tacky to the touch, more uniform in texture, and apparently less conducive to retaining its liveliness after repeated impacts. Hank Aaron himself famously observed within months of the transition: “If you hit the cowhide baseball once or twice, they go soft. There’s just no question about it.”
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In 1974, home runs across MLB declined by approximately 15 percent. Was the cowhide ball truly deader? Or were Aaron’s hands simply mourning the only material they had known for twenty years? The early cowhide covers were not yet optimized for baseball construction — the tanning and shaving processes that produce today’s cover were refined substantially over the next decade. And the players’ grip adjustments were real. By 1975, both leagues had fully transitioned, and the statistical environment had largely normalized. But the horsehide era was over, and with it went something that I am only partially able to quantify — a particular quality of feel, of aging, of the ball in the hand, that players who played across the transition still speak of with something approaching mourning.
SECTION XI
THE RAWLINGS ERA BEGINS - 1977 AND STANDARDIZED PRODUCTION
In 1977, Rawlings won the exclusive contract to manufacture all official MLB baseballs, ending a dominance that Spalding had maintained, in one form or another, since the 1870s. The departure of Spalding was not merely a business transition — it was the end of a manufacturing lineage that stretched back to Albert Spalding himself, the pitcher-turned-entrepreneur who had understood almost from the beginning that whoever controlled the ball controlled the game’s material identity. Rawlings brought tighter quality controls, more systematic testing protocols, and a manufacturing philosophy oriented toward consistency above all else.
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By 2000, production was consolidated entirely at a Rawlings facility in Costa Rica, dedicated exclusively to the manufacture of MLB baseballs. The Costa Rica facility introduced computer-monitored winding tension sensors calibrated daily — a level of manufacturing precision that would have been genuinely incomprehensible to the men who hand-wound balls in the 1890s.
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The interesting characteristic of the modern manufacturing era is this: the baseball has never been more precisely and consistently made than it is today, and it has also never been more aerodynamically mysterious. The precision of the Costa Rica facility did not resolve the ball’s capacity to produce unexpected effects. If anything, the reduction in manufacturing variation made those unexpected effects more puzzling — because they could no longer be attributed to production inconsistency. When the ball behaved strangely in the 2010s, we knew it wasn’t because of sloppy winding. The strangeness had to come from somewhere else.
SECTION XII
THE STEROID ERA AND THE BALL - AN UNEASY PARTNERSHIP (1994-2004)
The offensive explosion of the 1990s and early 2000s has been primarily attributed, in the public record and in the historical literature, to performance-enhancing drug use among hitters and to the altered training methods and pharmaceutical ecosystems of that period. I do not dispute that this attribution captures the primary driver. The bodies that were hitting home runs in 1998 and 1999 were not the same bodies that had been hitting home runs in 1978, and the difference was not entirely explained by diet and gym equipment.
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But the ball was also part of the conversation. Umpire Eric Gregg and several of his colleagues reported in the mid-1990s that the ball “felt livelier” than it had previously. Multiple anonymous player accounts from the period described a ball that seemed to jump off the bat with unusual authority on well-struck contact. No independent study definitively proved that the ball had changed — and Rawlings consistently denied that its manufacturing specifications had been altered — but the anecdotal claims were persistent and came from credible observers.
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Undoubtedly, the steroid era’s offensive numbers were primarily driven by chemistry in the body. But I cannot dismiss the possibility that a subtle and unmeasured change in ball liveliness was a contributing variable during some portion of this period. I also note that the expansion of the 1990s diluted pitching talent meaningfully, and that several of the era’s most famous offensive environments — Camden Yards, Coors Field, the old Bank One Ballpark — were structurally configured to promote offense in ways that had nothing to do with the ball’s construction. The steroid era was a conspiracy of causes. The ball may have been a minor conspirator. I have not yet found the evidence to convict it, but I have not entirely closed the file either.
SECTION XIII
THE SEAM HEIGHT QUESTION - AERODYNAMICS AND THE MODERN BALL
Seam height is the most consequential single measurement on the baseball — and also, historically, the most casually managed. The current MLB specification requires that seam height fall between 0.044 and 0.051 inches, a tolerance of just 0.007 inches. To give that number some texture: a human hair is approximately 0.003 inches in diameter. The permitted variation in seam height is roughly the width of two human hairs. This is, by any reasonable standard, a demanding specification. And it matters enormously.
A higher seam — toward the 0.051-inch end of the permitted range — catches more air as the ball rotates in flight. It creates more turbulence in the boundary layer around the ball’s surface, which increases aerodynamic drag. The ball decelerates faster and does not carry as far. For a pitcher, higher seams are a gift: better grip, better friction for imparting spin, more movement on curveballs and sliders, more sink on two-seamers. For a hitter, a ball with high seams may not fly as far on contact, but it arrives at the plate with more predictable movement and more identifiable spin.
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A lower seam — toward the 0.044-inch end — does the opposite. The ball cuts through the air more cleanly, reducing drag and allowing it to carry farther for equivalent exit velocity and launch angle. For a hitter in a launch-angle-optimized batting approach, a lower-seam ball is an ally. For a pitcher, it is an adversary: slicker to grip, less responsive to spin-imparting pressure from the fingers, less capable of the sharp late movement that makes breaking balls effective.
Seam height is arguably more consequential, pitch-to-pitch and game-to-game, than the the ball’s core. The COR determines how much energy the ball returns on contact with the bat. Seam height determines the aerodynamic environment in which that energy plays out over the 395 feet between home plate and the outfield wall. Both matter. But seam height is the more dynamic variable, more sensitive to small changes, and more difficult to monitor in real time. It has fluctuated outside acceptable tolerances repeatedly over the past decade without prompt league acknowledgment. History does not forgive us for not looking more closely.
SECTION XIV
THE GREAT HOME RUN SURGE - 2015 TO 2019
Starting in 2015, home runs in MLB began climbing in a manner that the sport’s analytical community immediately recognized as statistically anomalous. The increase was not the gradual drift that might be explained by evolving player development philosophies or roster construction trends alone. It was sharp, sustained, and league-wide. The record for home runs in a major league season was shattered in 2019, when 6,776 home runs were hit across both leagues — a figure that would have seemed like science fiction to anyone looking at the numbers from 2014.
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In 2018, Commissioner Robert Manfred commissioned a committee of scientists to investigate, chaired by Dr. Alan Nathan, Professor of Physics Emeritus at the University of Illinois — one of the foremost authorities on the aerodynamics of the baseball in the world. The committee’s Phase I report, delivered in 2018, reached a conclusion that the increase in home runs was due “nearly entirely to a change in the aerodynamic properties of the ball — reduced air drag.” The ball was carrying farther for the same exit velocity and launch angle. This was not a subjective impression. It was measured, documented, and confirmed.
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What the committee could not do was identify with confidence what had caused the reduced drag. It was not seam height alone, at least not as measured by the tools available. It was not the COR. It was not the ball’s weight. The ball’s outward specifications appeared largely unchanged. Theories included the possibility that the rubber pill was being more consistently centered within the wound ball since 2015, reducing wobble and asymmetric drag during flight, or that the ball was retaining its rounder profile through more of its trajectory. Phase II, delivered in December 2019, confirmed that drag reduction remained the primary driver of the 2019 home run surge — contributing approximately 65 percent of the increase — with changes in hitter behavior, particularly the widespread adoption of launch-angle-optimized swing mechanics, contributing the remaining 35 percent.
SECTION XV
THE 2021 DEADENING - LOOSENING THE FIRST WINDING
In February 2021, MLB sent a memorandum to all MLB clubs announcing deliberate changes to the ball’s construction, framed as an effort to reduce the wild home run fluctuations that had characterized the previous six seasons and to restore greater consistency to the offensive environment. The mechanism of the change was specific: Rawlings would loosen the tension on the first of the wool windings within the ball — the innermost layer, the one closest to the pill — thereby reducing the ball’s coefficient of restitution slightly and reducing ball weight by approximately 2.8 grams, less than one-tenth of an ounce.
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Independent laboratory testing found that the new balls would fly approximately 1 to 2 feet shorter on balls hit more than 375 feet — a difference that is negligible on a single swing but potentially decisive on the margin between a long fly ball and a home run over the course of a season. MLB also announced the expansion of humidor storage requirements from 5 to 10 ballparks. Humidors maintain baseballs at a consistent temperature and humidity — typically 70 degrees Fahrenheit and 50 percent relative humidity — preventing them from drying out and hardening, which makes them livelier. A ball stored in a dry environment is measurably harder and carries farther than a properly humidified ball.
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Pitchers noticed almost immediately. Lefty Blake Snell remarked that the laces on the new ball were thicker — that he could actually get a finger under the seam in a way that he could not with recent-vintage baseballs. Manager Joe Maddon of the Angels stated: “If in fact the ball doesn’t travel as far, that in and of itself will change the analytics of the game.” He was correct. The 2021 home run rate did drop measurably from the 2019–2020 peak, and pitchers broadly reported better command of breaking balls and two-seamers, consistent with the effect of higher, softer seams.
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SECTION XVI
THE 2021 DEADENING - LOOSENING THE FIRST WINDING
The baseball’s history is a mirror of the sport’s deepest tensions: the perpetual arms race between offense and pitching, between power and craft, between the desire to see the ball fly and the desire to see the ball dance. Every era’s defining statistics are inseparable from the physical construction of the ball that produced them. Ty Cobb’s singles game was not merely a product of Cobb’s genius — it was a rational adaptation to a soft, dark, misshapen ball in a low-light stadium in 1912. Babe Ruth’s revolution was not merely a product of Ruth’s supernatural physical gifts — it required a cleaner, firmer, livelier ball in a system that had just stripped pitchers of their primary defensive weapons. Bob Gibson’s 1.12 ERA was not merely a product of Gibson’s ferocious competitive intelligence — it required a 15-inch mound and an expanded strike zone operating in concert with a ball whose seam height was, for the time, unregulated. Mark McGwire’s siege on the home run record in 1998 was not merely a product of what McGwire was putting in his body — it may have been assisted, in some measurable fraction, by a ball whose aerodynamic properties were subtly but consequentially shifting. Aaron Judge’s 62-home run season in 2022 was not merely a product of Judge’s extraordinary combination of size, bat speed, and launch-angle discipline — it occurred in a ball environment whose drag characteristics had been deliberately altered fourteen months prior.
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The ball has never been passive. Even when the written rules were unchanged, the ball changed — in material, in winding tension, in seam height, in cover texture, in aerodynamic properties that our most sophisticated scientific instruments have, on multiple occasions, been unable to fully characterize. The ball has changed when manufacturers changed, when supply chains changed, when manufacturing processes were refined, when humidity varied, when storage protocols evolved. It has changed in ways that were announced and in ways that were not. It has changed in ways that were understood at the time and in ways that took decades to recognize.
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MLB should establish a permanent Office of Baseball Materials Research — independent, transparent, and publicly reporting — charged with monitoring the physical and aerodynamic properties of the official baseball in real time and communicating any meaningful changes to the public, the players, and the historians. We have the scientific tools. We have the manufacturing data. What we have lacked is the institutional will to treat the ball with the seriousness it deserves.
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Those baseballs in the Cooperstown vault are the same objects in name that Ray Chapman faced in August 1920, that Mickey Mantle drove into the upper deck on a May afternoon in 1956, that Mariano Rivera somehow cut across in that particular way that no one who studied it could entirely explain, that Shohei Ohtani launched into the California night on a low-seam ball whose drag coefficient had quietly shifted in ways that the best physicists in the sport had only recently begun to quantify.
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And yet it is not the same ball at all. The ball keeps every secret the game has ever tried to tell.
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NTSB North Texas Sports Blog
© 2026 North Texas Sports Blog | Feature written by Rob Olds at the NTSB Analytics Desk
Statistical sources: Baseball Reference, StatMuse, Baseball Almanac