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MLB Says It Didn’t De-juice the Ball. So Where Have All the Homers Gone?

Evidence shows that fly balls are behaving a lot differently in these playoffs. May that have changed the outcome of a series?

Getty Images/Ringer illustration

On Wednesday, with NLDS Game 5 tied 3-3 in the bottom of the ninth, Dodgers catcher Will Smith strode to the plate with two outs and one on. Clayton Kershaw had already blown sports history’s second-most-memed 3-1 lead, but Joe Kelly (and Dave Roberts) had yet to turn the tie into a four-run deficit, so Smith still had the potential to decide the series with one swing. For a fleeting second, Smith, the Dodgers, and undoubtedly a sizable percentage of the people watching at home thought he had.

Smith bat-flipped. Daniel Hudson spun. Play-by-play man Ernie Johnson raised his voice, ramping up for a timeless call. Several of Smith’s teammates vaulted over the dugout railing, preparing for a dogpile at the plate … and then the ball died on the warning track with Adam Eaton’s back to the wall, Johnson lowered his voice, and the disappointed Dodgers tried to drift back toward the dugout nonchalantly, as if they were just stretching or maybe making sure the railing was structurally sound.

A few more feet of flight, and Smith’s fly might have ended the suspense before Howie Kendrick could. Maybe the drama of the moment made Smith and his teammates misjudge the ball off the bat. Or maybe they were fooled because the ball behaved differently than it had during the regular season.

In August, A.J. Pollock hit a ball—I know, different from October already—that looked somewhat similar to Smith’s. That one traveled 13 feet farther and flew over the fence, forming part of the mental database the Dodgers were drawing on when they extrapolated the path of Smith’s liner from its initial launch.

I’m not going to tell you that these balls left the bats on the same trajectories or under identical conditions. Pollock’s ball went 1.6 degrees higher and 1.1 mph slower than Smith’s and stuck slightly closer to the corner. The wind wasn’t strong either day (at least at first pitch), but the temperature was a few degrees warmer in August. We don’t know whether Smith’s drive would have gone out if he’d hit it on August 20 or whether Pollock’s would have died had he hit his on October 9. But that’s kind of the crux of the issue: We don’t know. Because the difference could have been the ball.

Before the first wild-card game, I wrote about the possibility that the behavior of the ball would become a prominent postseason story line. Aided by a ball with reduced drag and increased carry, MLB batters hit 6,776 dingers during the regular season, 671 more than the previous record, which was set in 2017. According to calculations by multiple sources cited in that story, roughly 11 percent of the homers hit in 2019 would not have been bombs had the 2018 ball been substituted for the 2019 ball and everything else stayed the same.

Some of those additional dingers came on what looked like weak contact, which raised the specter of a pivotal postseason contest coming down to a lazy fly that would have stayed in the park in any other year. Referring to a late-September play in which Joc Pederson had bat-flipped in disgust, only to see a presumed easy out fly over the fence, I noted, “Were a similarly ball-dependent dinger to occur at a crucial time in October … it could embarrass MLB by swinging a series, slightly tarnishing a team’s victory, and giving fans of the defeated club more reason to be bitter.” The risk seemed to be that the changeable ball would distract us from the main event—the battle between the players—by tying the outcome of games not just to a contest of skill and a normal amount of randomness but to a piece of capricious equipment.

I was wrong about the ball—or, if we want to put it charitably, right in the wrong direction. The ball has become a story, but not because it’s flying so far. Rather, it’s looking significantly less lively than it has for a few years. No wonder the Dodgers went from frustrated bat-flips that accompanied homers to celebratory bat-flips that accompanied outs. Early this week, my Effectively Wild podcast partner, Sam Miller, and I discussed what seemed like a suspicious number of apparent long balls that had failed to clear the fence, and other fans and media members broached the same subject on Twitter. Those observations were all anecdotal, but on Thursday, Ringer contributor Rob Arthur published a study at Baseball Prospectus that strongly suggested that the ball’s drag spiked suddenly just as October began.

As he had in an April article that anticipated this season’s record homer barrage, Arthur used Statcast data to infer the drag of the ball from measurements of its progress between the mound and home plate. The higher the drag, the more speed the ball loses on its path to the plate, although drag-related differences are much more pronounced over the hundreds of feet that a fly ball carries than the roughly 55 feet a pitch covers between the pitcher’s hand and the plate. Arthur’s method is similar to one used by an MLB-commissioned committee of physicists, statisticians, and engineers that concluded last spring that the 2017 surge in home-run rate was largely attributable to decreased drag, although it couldn’t identify the attributes of the ball responsible for that lower air resistance.

Arthur concluded that the drag coefficient during the 2019 division series had climbed to a level not regularly seen since 2016, the year after the ball began to get goofy. He accounted for atmospheric effects (such as temperature and pressure), and the sample was sufficiently large to make it highly unlikely that the decrease could have occurred by chance. Arthur’s predictive model, trained on batted-ball results from the regular season, estimated that 50 percent more postseason homers would have been hit to that point if not for the mysterious uptick in air resistance. Max Muncy’s hard-hit fly out in Game 4, for instance—which appeared to leave Muncy, pitcher Sean Doolittle, and center fielder Michael A. Taylor bemused—would have had a 95 percent probability of clearing the wall during the regular season, according to Arthur’s computations.

Before that game (and days before Smith’s close call), Dodgers manager Dave Roberts brought up what he believed to be aberrant behavior in the ball.

According to Dodgers pitcher Ross Stripling, that wasn’t a universal sentiment. “We chatted about it in the dugout a little bit,” Stripling told me on Thursday. “Most people seemed to think the balls were the same. Rendon hit a home run [on Wednesday] at 96 mph into the marine layer at Dodger Stadium. That almost never happens. Enough evidence for me to think the balls are the same.” The October ball wasn’t dead enough to rescue Clayton Kershaw.

Players haven’t been as vocal about a difference in the ball this month as they were in the 2017 World Series, when multiple pitchers and coaches complained about the balls’ supposedly slicker surfaces, but the evidence for a related effect on home-run rate in that series wasn’t strong. The latest change may not be as obvious to the touch, but it does seem to be putting a damper on dingers, echoing an earlier decline toward the end of the season in Triple-A, where the MLB ball was used for the first time this year. When asked to comment on Arthur’s findings, an MLB spokesperson sent me the following statement:

The baseballs used in Major League Baseball are manufactured in batches. Balls that are used in the Postseason are pulled from the same batches as balls used in the regular season. Regular season and Postseason balls are manufactured with the same materials and under the same processes. The only difference is the Postseason stamp that is placed on the ball. As has been previously acknowledged, however, the drag of the baseball can vary over different time periods.

The statement is somewhat contradictory, in that it seems to simultaneously repudiate Arthur’s findings and allow that they could be correct. MLB acknowledges that the ball’s drag can vary, which indicates that Arthur’s analysis is plausible; his research suggests that the baseball’s drag jumped three times more from the end of September to the start of October than it ever varied from one week to the next during the 2019 regular season. Yet the statement also asserts that the only difference between the regular-season and postseason balls is the stamp. If the ball’s drag has varied that much, then the stamp almost certainly can’t be the only difference; something else about the ball must have changed to bring about that change in results. And because Arthur didn’t detect similar spikes at the start of previous postseasons, it must be something new.

Conspiracy theorists who suspect MLB juiced the ball back in 2015 as a fix for a low level of offense might also suspect that the league made the ball less lively now to avoid just the sort of stain on October that I had in mind last week (not to mention longer games that stem from increased scoring). MLB has consistently stated that it hasn’t intentionally tinkered with the ball, which is credible for a few reasons. Foremost among them is the fact that the MLB-sponsored panel of experts—many of whom are prominent members of the public baseball-analysis community—hasn’t yet determined why the ball is behaving differently. It’s tough to see how MLB could be engineering a desired change in home-run rate without understanding what’s making the balls behave the way they do. More likely, the latest changes are unintended byproducts of a tightening in the baseball’s specifications that the committee recommended, which was reportedly implemented after MLB acquired baseball manufacturer Rawlings last year.

Commissioner Rob Manfred noted last month that he had reconvened the committee and requested a fresh report, which he expects to receive shortly after the World Series. “We need to see if we can make some changes that gives [sic] us a more predictable, consistent performance from the baseball,” Manfred said. One member of the committee told me last week, “There is still uncertainty about what is causing the changes, but we’re getting closer.”

It seems to be in MLB’s best interests to speed that process along. Frequent fluctuations in the ball’s behavior—whether within or across seasons—may undermine consumer confidence in the consistency of the sport. It’s far from certain that an alteration to the ball affected the outcome of the NLDS; for one thing, if the ball were carrying the way it was in September, Kendrick might have hit a homer even earlier in Game 5.

Even so, the possibility persists. Although Arthur didn’t draw an explicit connection between his results and Smith’s near homer, many of his followers made that leap on their own:

Whether the next whiplash leads to more homers or fewer, it can’t be beneficial for the ball to be in the back (or the front) of fans’ minds whenever they see a liner sneak over the wall or fall just short. It’s jarring enough from a spectator’s perspective for the offensive environment to morph drastically from season to season, but it’s even more difficult for fans to recalibrate when the change occurs six months into a seven-month season, just as the stakes increase. Nor is it fair to teams, players, and agents to keep changing baseball’s meta without providing patch notes, considering that the behavior of the ball can impact players’ incentives, approaches, and financial rewards and alter team’s talent evaluations and roster-construction strategies. Can we really blame Ronald Acuña Jr. for not hustling on what he thought was a homer in NLDS Game 1, or should we blame the ball for deceiving him?

While some variation in the ball’s behavior is acceptable, its recent volatility and rise into extreme territory doesn’t reflect well on the league. If we rule out a far-fetched conspiracy, the only alternative explanation for the fickle ball is that MLB can’t control the behavior of the sport’s most important piece of equipment. In a way, that’s worse than the existence of some baseball-construction cabal, especially considering that MLB now directly controls the production process. Nor is it healthy to have prominent players accusing the commissioner of lying (which the league doesn’t like). Technology has made it more difficult for MLB to keep the ball’s behavior close to its vest: Just as it was untenable to bar replay review after TV allowed fans to scrutinize umpires’ mistakes, it’s untenable to pretend that the ball is a constant when public data says different.

“If we make a decision to change the baseball, you’re going to hear about it,” Manfred said in July, adding, “We would do it in a way that was transparent to the media and the fans in advance.” While openly advertising a change to the ball might invite a backlash from some quarters, the precedents are instructive: NPB’s secretive tweaks in 2013 caused a scandal, while the NCAA’s public ball change in 2015 was warmly received.

The postseason is exciting, regardless of how many homers are hit. But greater transparency—perhaps public testing for juiced balls as well as juiced batters—would put a stop to the suspicion and free us from questioning the conditions of baseball’s biggest games. The hubbub about the ball won’t go away until the mystery is solved and the home-run rate reaches equilibrium. Only then will we hear “Play ball!” without wondering, “Which one?”