- An astrophysicist has collected and taken apart MLB game balls for years, looking for changes.
- She found MLB secretly used two different balls, one lighter than the other, in 2021.
- MLB acknowledged using different balls but blamed it on COVID-19-related production issues.
Sean Doolittle has pitched across 10 seasons in Major League Baseball with four teams. He’s made two All-Star teams and gunned down the best lineups on the sport’s biggest stage on the way to a world championship. He’s also been the losing pitcher in an elimination game and been kicked off the roster during a prolonged slump. In other words, he’s come about as close as one can to seeing all American baseball has to offer.
But as accustomed as Doolittle is to baseball’s ups and downs, there is one part of the sport that he says becomes less familiar every season: the baseball itself. The namesake and fundamental implement of his sport — a tool he has gripped and thrown more than 7,000 times — has in recent years begun to behave in ways that defy his finely honed sense of its character.
“I feel like I normally have a pretty good handle on being able to judge a fly ball or a line drive, like a ball in the air to the outfield,” Doolittle, now a free agent hoping to bounce back after an up-and-down stint between the Cincinnati Reds and the Seattle Mariners, told Insider. “There were a few instances over the course of the  season where, you know, we’re sitting in the bullpen watching the game or whatever. And, like, a home run gets hit, and you’re kind of, like, surprised that it got out. And so, like, you’re looking at it and you’re like, ‘That’s kind of weird.’ … It can only happen so many times before you start, like, questioning things.”
It isn’t just the odd home run that gives Doolittle reason to question the baseball. League balls are made by hand in a Rawlings factory in Costa Rica; each one exhibits minor variations from the next, and manufacturing protocols have changed over the decades. In February, the league revealed that, on the advice of its cadre of scientific experts, it had secretly begun making the ball’s center — the layered complex of yarn wound around a cork and rubber core that you find beneath the leather exterior — slightly lighter and less dense “in order to improve the consistency of the baseball’s performance.”
Specifically, the league said, Rawlings didn’t wind the yarn as tight as before. The new, looser balls came off the bat softer, the league said, ultimately traveling shorter distances — welcome news for pitchers dealing with the ramifications of the most homer-happy era in the sport’s history. These new and improved balls, the league said in an internal memo explaining the move, would be introduced in the 2021 season.
Do you have information to share about Major League Baseball or Rawlings and changes they have made to the baseball? Contact Bradford William Davis confidentially at [email protected] or via Signal at (646) 481-0859.
But for Doolittle, the baseball’s performance in 2021 was anything but improved. He brings up Joey Votto, his prolific Reds slugging teammate who enjoyed a seven-game home-run streak in July.
“The first homer he hit to start that streak was an opposite-field homer in Cincinnati that carried out to, like, straightaway left field,” Doolittle said, describing it as a “weak fly ball” that shouldn’t have made it over the wall. Thanks to the advent of publicly available analytics measuring how hard the ball was hit (exit velocity) and the trajectory (launch angle), you don’t have to take Doolittle’s word for it. The fly ball Votto struck had a .082 xBA and 8% home-run probability, meaning that more than nine times out of 10, a ball hit that hard and that high gets caught in the outfield, not in the cheap seats.
Then, after six more games of home runs, Votto’s fortunes turned in the opposite direction. He hit a scorching 110-mph blast at an optimal 24-degree angle that, by the numbers, had a 92% shot at clearing the fence. Instead, it somehow smacked the wall for a single, ending what could have been a record-breaking streak.
The nonplussed star’s verdict at the time: “That’s baseball.”
But according to independent research viewed exclusively by Insider — and confirmed by MLB — there is a possible explanation to the puzzle of Votto’s streak and all the weirdness Doolittle sees. It’s not baseball — it’s baseballs. Plural.
2 different balls with different performance profiles
According to a new study by Meredith Wills, a Society for American Baseball Research award-winning astrophysicist, the league used two distinct types of baseballs — one lighter and deader than the other — during the 2021 season. By dissecting and carefully measuring hundreds of balls used in 15 major-league parks, Wills found that the league did indeed introduce a new ball with a lighter center, as it pledged to do in the February memo. But she also found that MLB continued to use the older, heavier-center ball at the same time, apparently without telling fans, clubs, or players.
Wills’ findings could have far-reaching implications for the sport, shattering what little trust and goodwill remains between league officials and players, whose fortunes rise or fall on minuscule and obscure details like the weight of a baseball’s center. Informed by Insider that the league sent teams two different balls with different performance profiles, players, scouts, and front-office staffers expressed bafflement and frustration. “There’s a lot of things that … the public doesn’t really see,” said one National League outfielder who asked not to be named. “There’s just, like, lack of transparency, with [these] issues. And, you know, I don’t know why that is.”
Wills, whose work to reverse-engineer the design and manufacture of baseballs has been covered in Sports Illustrated and The Athletic, has been collecting and deconstructing game balls since 2018 to track changes that the league — which purchased Rawlings in 2018 alongside a private-equity firm — makes. When Wills took apart balls used last season and weighed their centers, she found that just under half clustered at about 124 to 125 grams, roughly in line with the league’s new process for balls with a lighter center. The other balls, however, had centers clustered at about 127 grams, consistent with all the baseballs she had cut open from the previous 20 seasons.
It’s important to note that all the overall ball weights were within the 5 to 5 1/2 ounces that league rules permit, and that one would expect to see some variation in a handmade product. But the differences Wills found aren’t random. Inside the Rawlings balls’ leather coverings are batch codes — seven stamped letters that indicate the production week, a receipt that allows an exceptionally curious person to know the date the ball was manufactured.
If the weight variations were random, then one would expect them to be evenly distributed across the various manufacture dates. But they weren’t. Wills immediately noticed a pattern: The baseballs with heavier centers were manufactured during distinct periods from those with lighter centers. (Insider reviewed Wills’ ball data, including the batch codes.)
Looking at the batch codes, Wills could see that Rawlings had apparently alternated between making balls with heavier and lighter centers since late 2019, when it started production for the 2020 season. And while the league claimed in its memo announcing the newer balls that it had “directed” Rawlings not to ship any of the new baseballs “for regular season or postseason game use in 2020,” Wills found that at least 15 balls with the new, lighter centers had somehow turned up at ballparks throughout the 2020 season. Her conclusion: MLB manufactured two different baseballs for the 2021 season, one bouncier than the other, even though the league told teams in February that the new, less-bouncy, lighter-center ball met “all of our performance specifications” and would be used for the new season.
In a statement, MLB confirmed Wills’ findings: It did indeed use two different balls last season. “Every baseball used in a 2021 MLB game, without exception, met existing specifications and performed as expected,” the league said. But after approving the shift to the new “re-centered” ball for 2021, it said, COVID-19 forced Rawlings to backtrack and use older balls to cover for production delays. “Rawlings manufactures Major League balls on a rolling basis at its factory in Costa Rica,” it said. “Generally, balls are produced 6-12 months prior to being used in a game. Because Rawlings was forced to reduce capacity at its manufacturing facility due to the COVID-19 pandemic, the supply of re-centered baseballs was not sufficient to cover the entirety of the 2021 season. To address this issue, Rawlings incorporated excess inventory into its shipments to Clubs to provide a full complement of baseballs for the 2021 season.”
The statement said that the league informed both its independent panel of experts on the baseball as well as the MLB Players Association — the union representing big leaguers — of the decision to use old and new balls at the same time and that the “2022 season will be played with only balls manufactured after the production change.”
MLB’s explanation sounds reasonable, but it doesn’t fully explain Wills’ data. She found that Rawlings first began shifting production to the new balls in October 2019, more than a year before the February 2021 memo acknowledging the production change. It switched back to making the old ball in January 2020,— three months before lockdowns began in earnest and six months before Costa Rica’s reported daily case count cracked 100, according to Google’s COVID-19 data. It switched to the new ball again in October 2020. But Wills found that Rawlings switched back to the old ball again after January 2021 — every ball Wills has found made after that date had the older, heavier center, including balls made as recently as August. It’s hard to see how these qualify as “excess inventory” — the batch numbers indicate that they were made after the league had announced the switch to lighter centers.
As for the league’s contention that it informed the union, if that’s true, it doesn’t appear that the information reached the players themselves. None of the 10 players reached by Insider for this story were aware that they had been playing with two different balls. The veteran pitcher Andrew Miller, a union leader who is deeply engaged in ongoing negotiations with the league over the next contract, said: “I’m not sure what we were told, but I’d assume it was nothing. If the balls meet standards, then they would have no reason to tell us anything.”
Alan Nathan, an esteemed physicist who advises the league on changes to the baseball, declined to comment when asked whether he’d been made aware of the league’s decision to use two balls. “I prefer to leave any comment about the baseballs to MLB and/or Rawlings,” he said.
Whatever MLB’s reason, Wills’ research and the league’s acknowledgment finally confirm Doolittle’s suspicions about the ball. It bounced differently because there were, literally, different balls.
‘The ball is the game’
Athletes across all sports have an understandable focus on the exact specifics of the equipment they are using. Any potential change in the ball’s performance matters. Tom Brady’s sense of feel for the ball is so important to his game that he was accused of instructing New England Patriots staffers to release a minute yet, to his touch, detectable amount of air from the balls he would use in a critical playoff match against the Indianapolis Colts in 2015, a game the Patriots dominated 45-7. The tampering, which exploded into an investigation that eventually led to Brady’s suspension, introduced “Deflategate” into the American sports lexicon.
In 2006, with limited input from players, the NBA initiated a league-wide change from its classic leather Spalding ball to one that used a cheaper synthetic material. The players despised the slippery, gripless ball enough to file a grievance with the National Labor Relations Board. “In hindsight, we could have done a better job. I take responsibility for that,” said David Stern, then the NBA commissioner. The NBA scrapped the experiment midseason.
—Kendrick Perkins (@KendrickPerkins) May 13, 2020
More recently, when the NBA switched to a new manufacturer, Wilson, it tried to avoid its past mistakes by looping in the players. But after the change, the league’s 3-point percentage dropped to its lowest rate since the 2016-2017 season. Perennial All-Stars such as Paul George, Joel Embiid, and reigning MVP Nikola Jokić were swift and vocal critics of the new ball.
However insignificant the changes to a ball may appear, especially to outsiders, athletes care. A lot.
When one National League pitcher became aware of Wills’ findings, he was so intrigued that he tried to replicate them himself using balls he brought home for the offseason. Wills told him how to do it: Use a kitchen scale to weigh a mix of a half-dozen 2021 MLB baseballs from a single game. Then, using a pocketknife, carefully remove the leather cover, and record the batch code printed on the inside and center weights. Wills told the player he should expect the centers to fall into two weight ranges: “124-125g” and “around 127g.”
The pitcher, who asked not to be named, texted Wills pictures of the six balls on his scale, which he shared with Insider. There were four balls with centers weighing within a tenth of a gram of 127 grams, and two between 124 and 125 grams — exactly in line with Wills’ predictions. “Weird,” the pitcher remarked.
Insider spoke with 24 people across MLB including players, coaches, scouts, and senior front-office workers, most of whom reviewed Wills’ research. Many requested anonymity for fear of reprisal from the league. They expressed a mix of surprise, alarm, curiosity, skepticism, and frustration with the way the MLB had handled production of the baseball.
“Yeah, that’s a big breach, for me, of competitive integrity,” one American League scout said. “It is a situation where the game plays differently, and there’s a reason that’s not random or aleatory. The game is being made to play differently because they’re tampering with the ball.”
This is no small charge. In 2013, Ryozo Kato resigned as commissioner of Nippon Professional Baseball — Japan’s top professional league — after acknowledging the league had introduced a new baseball that dramatically increased home-run rates without informing the players. NPB’s lack of transparency around the switch infuriated its players union, which called for Kato’s resignation. Kato maintained that he was unaware the league was using a new ball but nonetheless said he “caused a lot of problems over the ball, and that was a huge reason for my decision” to leave.
“Even if it’s not on purpose,” the scout added, “It’s exactly the same as throwing a foreign substance on the ball” — a pointed reference to the league’s crackdown on pitchers using foreign substances to get an edge on hitters by improving their grip. The league’s enforcement of rules against “sticky stuff” in 2021 resulted in multiple suspensions.
“It creates the same effect, [in] that it changes the way the ball plays,” the scout said. “And the ball is the game.”
“You would like to have some consistency,” said Yankees second baseman DJ LeMahieu. “I don’t think it’s that difficult to have pretty consistent baseballs year in and year out.”
“Everything in this game is based on your statistics,” said Adam Ottavino, a free agent who last pitched with the Boston Red Sox. “There’s a million of them. If the variables are being changed out from underneath you and in an unfair way, that sheds doubt on every statistic that you have.”
Ottavino can speak in spectacular detail about the mechanics of any given pitch, but when it comes to the baseball itself, he says players “don’t know jack shit.”
“You’re just basically believing at face value what they tell you,” he said. “Which is probably not what we should be doing.”
While players expressed frustration with the league, front-office staff were more diplomatic. Insider spoke with 14 MLB front-office workers from 11 big-league teams; all confirmed that their understanding entering the season was that MLB was manufacturing one baseball made under one set of guidelines.
One senior American League executive told Insider they didn’t feel comfortable commenting about the production of the baseball. “They send us baseballs, we prepare them as instructed, and then we go out there and we play the game,” the person said. “And, you know, we have to have faith in the league and everybody else to provide us with a consistent baseball.”
‘Major League Baseball’s turning this game into a joke’
Wills’ discovery is hardly the first controversy surrounding the production of baseballs. After a relative historic lull in offense going back to 2009, baseballs started flying out of ballparks at unprecedented levels beginning with the second half of 2015, a trend that led to charges that the league had intentionally “juiced” the ball. In 2018, MLB teamed up with the private-equity firm Seidler Equity Partners to purchase Rawlings, its official and exclusive game-ball manufacturer, for $395 million. The MLB executive vice president Chris Marinak said the acquisition gave the league “more input and direction on the production of the official ball of Major League Baseball,” which he called “one of the most important on-field products to the play of our great game.”
Then 2019 happened.
Balls flew at an unprecedented rate: 6,776 home runs in total, 671 more than the league’s record. Before a June game against the Yankees — one of four teams that broke their franchise home-run record that year — the Astros ace Justin Verlander told Insider the league was “juicing the balls.”
“After seeing thousands of balls hit off the bat in my career, you kind of know what’s a home run or what’s not,” Verlander said at the time. “And then all of a sudden, like, some iffy ones started being homers. And then some like, what the hell is that ball doing, going out?” Despite having a personally dominant year that would eventually result in Verlander’s second American League Cy Young Award, he was even angrier in an interview with ESPN’s Jeff Passan, arguing that the rise in home runs had become “a fucking joke.”
“Major League Baseball’s turning this game into a joke,” Verlander said a day before the 2019 All-Star Game, which he was scheduled to start. “They own Rawlings, and you’ve got Manfred” — the MLB commissioner, Rob Manfred — “up here saying it might be the way they center the pill. They own the fucking company. If any other $40 billion company bought out a $400 million company and the product changed dramatically, it’s not a guess as to what happened. We all know what happened.”
At the time, Manfred did not publicly respond to Verlander’s comments but said there was “no desire on our part to increase the number of home runs.”
Then, after the record-setting regular season, balls that practically floated into the cheap seats were dying at the warning track throughout the playoffs. The Baseball Prospectus writer and data scientist Rob Arthur studied the results of 800 playoff fastballs and found the “drag” was much lower than the regular season. In an article headlined “The Rocket Ball has Disappeared,” he wrote that “almost overnight within the same season, the ball has been replaced by one with wholly distinct characteristics, ranging from the speed with which it leaves the bat to the distance it travels.”
Fast-forward to February 2021. Wills, who at that point had been unstitching baseballs and publishing her findings for three years, began to find that balls with consistently lighter centers had been used in the 2020 season. Shortly after Sports Illustrated’s Stephanie Apstein approached MLB for comment on Wills’ research, the league sent out its memo to teams acknowledging the lighter centers and claiming that they had been authorized for use only in the coming season.
Nathan, the independent expert who advises the league, echoed the memo in a statement to Sports Illustrated. The lighter centers were the result of a “process change,” he said, imposed to bring the baseball “closer to the mid-range of the MLB specification.”
A looming lockout
As of this writing, the league and the MLB Players Association are on the verge of a lockout as they attempt to negotiate a new collective bargaining agreement.
The union declined to comment on MLB’s acknowledgment about last season. But players who talked to Insider believe the league’s lack of transparency about the baseball is also a labor issue.
“There’s a fair amount of distrust between players in the league on certain topics, and this is one of them,” the union leader Miller said. He doubted the union had much say in the matter, since at the end of the day all the balls met established parameters in the rulebook. “But I think now we know what we know about how small the change in the baseball can greatly affect the way it travels, the way it’s thrown, or its ability to be gripped or whatever it is — like, those parameters may be pretty wide. And if there’s room for manipulation, that is concerning.”
Miller is not alone. “The specs on major league baseballs, they almost don’t deserve to be called specs,” Nathan said in an interview for the 2012 book “Extra Innings.” “They’re so loose that the range of performance from the top end to the bottom end is so different.”
“I kind of feel like pitchers were being punished for giving up an increased number or percentage of home runs on their stat lines,” Doolittle said, remarking on the home-run boost. Doolittle argues that relief pitchers, who enter the game in short spurts after a starting pitcher’s work is done, are particularly vulnerable to a surprisingly bouncy baseball taking money out of their pocket.
Some players told Insider they would like to see the players union address any economic implications of ball variance head-on in their negotiations. According to The Athletic’s July report on the ongoing discussion, 2022 baseballs are already being manufactured.
The National League pitcher who replicated Wills’ study wants to see the union and league agree upon some form of quality control. “You can’t tear up the baseball before the game,” he said. Instead, he suggested having someone designated at every ballpark “who weighs the baseballs” designated for that game and reports them somewhere appropriate.
‘Do they know what’s going on?’
While the league blames COVID-19 for the dual-ball season and says it won’t happen again, some of the players reached by Insider entertained more conspiratorial hypotheses. For example: What if MLB sent a disproportionate number of either ball to a specific park or for a specific set of games, putting its thumb on the scale to create more or less scoring?
The National League pitcher who replicated Wills’ study believes MLB “is more or less incentivized to introduce two baseballs” to try to produce higher- or lower-scoring games.
“You know, send a bouncier baseball, lighter baseball — whichever flies more — to a primetime series,” he told me, listing off marquee matchups like Yankees-Red Sox and Mets-Phillies. “Then,” he suggested, send more dead baseballs to “Texas versus Seattle. Or, you know, Detroit versus Kansas City. No one’s going to bat an eye.”
On the other hand, he speculates, the league could flip that approach around and send high-octane balls to low-profile games and “produce more offense,” which might “put more seats in the stands — just continue to bring up fan engagement.”
Doolittle believes that using two balls could have massive implications for the league’s emerging gambling partnerships.
“There’s a lot of money at stake there … I can’t believe we’re talking about this,” the veteran said, interrupting himself out of disbelief over what he was about to suggest. “But, you know, like, setting odds and stuff like that. And like, do they know what’s going on?”
To be clear, there is no evidence to support these theories. Wills — who relies on a nationwide network of ballpark spies to surreptitiously swipe game balls and send them to her for dissection — has collected enough balls to document two distinct varieties, but because MLB uses about 900,000 balls a season, a study like hers can’t determine whether either ball was sent disproportionately to a specific team or game.
The National League pitcher imagined a good-faith explanation: MLB experimenting with the ball in an earnest search to find the best mix of run-scoring and action on the field to “make the game better.” But without team or player consent, such an approach would still rub him the wrong way.
If it is an experiment, it may be ongoing: During the annual meeting between the league franchise owners in November, Manfred floated the possibility of changing the ball yet again — proposing using a tackier leather that the league says will allow for better pitcher grip without the “sticky stuff” that provoked crackdowns during the season.
“We could be in a position to use a new ball next year,” Manfred said. “Maybe it’s going to be ’23 instead, but we’re continuing to work on it.”
Doolittle is at least familiar with some of the league’s prototypes, as he recalls players being invited to test them in previous seasons. Still, he wants more: “I’m not saying [player input] doesn’t happen,” he said. “But that’s the only instance that I know of.”