Why Are MLB’s Base Hits Disappearing?

On August 6, a slumping Christian Yelich got a gift from White Sox left fielder Eloy Jiménez, who misread a slicing fly ball off Yelich’s bat and allowed it to fall fair. When Jiménez’s momentum carried him into the netting intended to protect fans—remember fans?—Yelich kept running and rounded the bases for an inside-the-park home run.

For Yelich, who’d been benched in the Brewers’ previous game, Jiménez’s miscue was a rare exception in 2020; nearly every other ball he’d put in play this season had found a fielder. Yelich added two over-the-fence homers in his next three games, and his numbers in some stat columns are back to being MVP-caliber, but his batting average still sits at .149.

Yelich’s slash-line-sabotaging batting average is the product of two culprits: an elevated strikeout rate, and a low batting average on balls in play. In both respects, his season is a microcosm of major league offense this year. Despite the addition of the National League DH, hitters have struck out in 23.7 percent of their plate appearances so far, up from 23.0 percent last season. That isn’t so surprising, considering the sport’s strikeout rate has risen for 14 straight summers. What is surprising is MLB’s batting average on balls in play: .276, down from .298 in 2019. Thanks to that precipitous drop, the league as a whole is batting .230, seven points lower than it did during 1968, the “Year of the Pitcher.” As one front-office analyst says, “It doesn’t pass the sniff test for real baseball.” Almost every aspect of this pandemic-delayed, desperately reconfigured, competitively compromised campaign is emitting odd odors compared to past years, but the big BABIP dip is one of the season’s most mysterious smells.

Although Jiménez’s nothing-but-net play, Jo Adell’s off-the-glove four-base error, and Hunter Pence’s no-hitter-attempt-ending failure to find a fly ball have added a few fielding flubs to future blooper reels, hitters haven’t been rewarded for embracing the baseball cliché that claims, “When you put the ball in play, good things can happen.” For decades, MLB’s BABIP has been remarkably consistent, despite any number of potentially paradigm-shifting developments: expansion, PEDs, new ballparks, shape-shifting strike zones, the sabermetric movement, data-driven defensive positioning, changes to the ball, the “fly ball revolution,” and so on. From 1993 to 2019, the seasonal BABIP never sank below .293 or climbed above .302. In that context, the current .276 is striking, small sample notwithstanding. We’re only a quarter of the way through the scheduled regular season, but this level of offensive futility on balls in play is already anomalous.

From Opening Day through Sunday, major league games took place on 18 consecutive days. The chart below shows the leaguewide BABIP over every in-season stretch of 18 game days—consecutive or otherwise—dating back to the beginning of 1995.

In those 25 full seasons since the strike, MLB’s BABIP never dipped below .283 in any stretch of 18 game days. Not since September 1991 has MLB’s BABIP been as low as .276 over any equivalent span. Granted, this latest stretch of 18 game days has yielded fewer plate appearances and batted balls than the average stretch of 18 game days, both because of COVID-caused cancellations and because of the record strikeout rate. Still, this stubbornly low BABIP has persisted over more than 16,000 plate appearances and more than 10,000 batted balls, so it’s probably not purely a fluke. To make matters more perplexing, one might have expected that the universal DH would buoy BABIP in light of the ineptitude of pitcher hitters, although the NL and AL have boasted identical BABIPs dating back to 2002. Plus, the warm months of July and August are typically the peak period for BABIP, so any weather or temperature effect should be acting in the opposite direction of this downturn.

Relative to last season, BABIP is down by between 17 and 23 points on ground balls, fly balls, and line drives. It’s down for left-handed hitters and right-handed hitters, albeit more for the former. It’s down in every inning, although the dips in the first two innings have been particularly pronounced. Pick a split or a circumstance, and hitters are having a harder time getting hits, which has flummoxed front offices. Another team analyst notes, “The most likely explanation is that it has to do with the shortened season, or the fans being gone. Something about this whole COVID situation.” But nobody seems to have narrowed things down. “Haven’t been able to come up with any single great explanation,” an R&D director says. “Might be a confluence of a number of things. But it’s super weird.”

Once the ball is put in play, only a few things can affect whether it falls for a hit—how well it was hit, whether there’s a fielder close enough to catch it, and whether the fielder is good at his job. Assuming luck can’t entirely explain what we’ve witnessed, then, the BABIP dip must be attributable to one or more of the following factors: weaker quality of contact, improved defensive positioning, and enhanced fielder performance. Let’s take them one at a time.

“We’ve kicked around some ideas like hitters not getting looks at pitchers other than their own teammates in summer camp and how that might impair their readiness,” says an assistant GM. There are some signs that hitters haven’t been themselves. Collectively, batters have swung through a much higher percentage of pitches in the strike zone than they did during any previous full season in the pitch-tracking era, even as more low strikes are called against them. More than twice as many of their hard-hit balls have been popups as in any other Statcast-tracked season. They’ve also pulled a higher percentage of their ground balls. Past research has suggested that when the effect of temperature is controlled, hitters tend to be ahead of pitchers early in the year, but maybe this season’s suspended spring training, long layoff, and brief summer camp left hitters ill-prepared to time big league pitching. And although pitchers have broken down at a disturbing rate this season, those who have held up may be as nasty as ever. “Pitchers aren’t prepared to go deep and stay healthy,” says one team’s special assistant to the GM. “But that may be different than being prepared to get hitters out.”

What’s more, lighter workloads for starting pitchers have deprived hitters of repeat looks at opponents: Relievers have thrown 45.7 percent of all innings this season, up from 42.1 percent in 2019. Last year, pitchers allowed a .250 batting average, a .318 wOBA, and an 88.6 mph exit velocity during their first and second times through the order. After that, those figures rose to .269, .335, and 89.1. But this season, hitters haven’t had many chances to feast on stuff they’ve seen before: Only 8.1 percent of all plate appearances in 2020 have come when facing an opposing pitcher for the third time or more in the game, down from 13.0 percent last season. So while this season’s average fastball velocity (93.6) is identical to 2018’s and 2019’s, hitters have been confronted more frequently with unfamiliar arms.

According to MLB’s Statcast compendium Baseball Savant, the average exit velocity of all batted balls is down by almost a mile per hour relative to last season, which would suggest that batters aren’t hitting the ball as hard. Softer batted balls might mean easier fielding opportunities, which would bring down BABIP. But between 2019 and 2020, MLB Statcast’s tracking technology changed from TrackMan to Hawk-Eye, which complicates cross-season comparisons.

Hawk-Eye is capable of recording a higher percentage of batted balls than TrackMan was, and the popups and dribblers that Hawk-Eye is better-equipped to capture could be reducing 2020’s average exit velocity compared to those of past seasons. If we limit our sample to batted balls between zero and 40 degrees, which are more likely to be captured by both systems, this year’s average exit velocity is still down, but by only about half a mile per hour, placing 2020’s average exit velocity between 2015’s and 2018’s. (Another complication: MLB quietly installed potentially exit-speed-suppressing humidors in Fenway Park, Citi Field, and T-Mobile Park prior to this season, extending a list of humidor-equipped parks that previously included Coors Field and Chase Field.) In addition, the aerodynamic drag of the ball has reportedly increased to 2018 levels, which wouldn’t affect exit velocity but would cause batted balls to slow down faster and carry less far.

The problem with pinning all of the blame on overmatched batters and a less lively ball is that in previous seasons with similar exit velocities and aerodynamic drag, BABIP didn’t drop. In 2018, exit velocities and drag were nearly identical to what they are now, but BABIP was .296. In 2015, exit velocities were lower and drag was higher than in 2020, but BABIP was .299. There doesn’t seem to be an ironclad cause-and-effect connection. There’s also the pesky fact hitters’ outcomes have declined even when we hold batted-ball characteristics constant. For instance, on balls hit between 90 and 100 mph and between -10 and 10 degrees, the leaguewide batting averages in 2018 and 2019 were .435 and .428. On balls in that same bucket in 2020, batters have hit .369. So even when batters are launching balls with roughly the same speed and trajectory, they’re making outs more often.

Fine, then: This must have something to do with defense. “Maybe it’s more about the positioning than anything,” says former outfielder Sam Fuld, now the director of integrative performance for the Phillies. “We’re positioning in the outfield deeper and deeper, so with a deep outfield and less juiced baseball, maybe that plays a big role. And there is a big uptick in infield shifting this season.” This year, teams have shifted their infields on 35.8 percent of all pitches, up from 26.2 percent of all pitches last season. They’ve also gotten slightly more aggressive with extreme outfield alignments. Shifting more isn’t always beneficial, but Sports Info Solutions credits teams in 2020 with more than 22 percent of last season’s total infield shift runs saved in fewer than 9 percent of the innings. And it does seem as if BABIP has fallen even further with the shift on than without the shift.

Here’s the nitpick with the positioning hypothesis: This isn’t the first time that shifting has increased. In fact, infield shifting increased more steeply on a percentage basis from 2018 to 2019 than it has from 2019 to 2020. More broadly, with the exception of a plateau in 2017, the shift rate has risen every year for the past decade. And throughout that time, overall BABIP didn’t budge: The league average was .297 in 2010 and .298 in 2019. Other changes in the game could have hidden the shift’s macro effects, and maybe teams in 2020 are shifting not only more often, but also more efficiently. But could shifting have gone from almost unheard of to happening more than a quarter of the time with no discernible impact on leaguewide BABIP, only to cause a cratering BABIP with one more boost to the tactic in 2020? “Not impossible, I guess, but I would be extremely skeptical that that is the answer,” says the special assistant.

Let’s consider one more theory. Last week, the Wall Street Journal’s Ben Cohen and Joshua Robinson reported that basketball and soccer players have shot free throws and scored on free kicks, respectively, more reliably in post-pandemic games. They attributed that improvement in marksmanship at least partly to reduced distraction as a result of the absence of fans. The same effect might apply for fielders: In quieter ballparks, fielders theoretically could gauge hit hardness better based on the crack of the bat, call for balls (or call off other fielders) without being drowned out by the crowd, or catch foul popups with less auditory or physical interference. “If anything, you can hear your teammates yelling ‘in’ or ‘back’ a little quicker/easier,” Fuld says.

Just as hitters prefer a plain, dark background for a batter’s eye, it’s possible that fielders in fan-free stadiums would have a better backdrop against which to pick up the ball. It’s not unheard of for fielders to complain about losing balls in a sea of white shirts, although Fuld says fan glare is a non-issue for fielders in most stadiums and notes that the cardboard cutouts currently filling in for fans can create glare of their own. Lastly, fielders might feel less fatigued than they would in a normal-length season, making them fleeter of foot.

It’s difficult to separate defensive positioning from defensive performance using publicly available data. One way we can try is by comparing success rates on plays of various difficulty levels via Baseball Savant’s outfield catch probability leaderboard. This data accounts for player positioning and batted ball trajectory, so it should isolate how well outfielders are getting to balls regardless of how much ground they have to cover.

In every bin except five-star plays (which is still a minuscule sample), outfielders have been better at catching balls than they were last year, independent of positioning, although MLB senior data architect Tom Tango cautions that the standards for the star categories fluctuate from year to year, which may make those comparisons less meaningful. MLB was unable to provide any data on average “jumps” for fielders, which might shed light on whether they’re reacting more quickly or taking more direct routes.

So, have we hit on the answer, or is our batting average off also? “It’s such a huge difference it’s hard to believe any one of those things could be it,” the R&D director says. Maybe it’s a mixture of all of the above: disadvantaged hitters, more adeptly positioned fielders, and more adeptly performing fielders, all sprinkled with a dash of 2020 chaos. Whatever the cause (or combination of causes), 2020’s low BABIP has plunged the league’s average runs scored per game to its lowest level since 2015, despite a still-high home run rate. It’s also exacerbated MLB’s trend toward less contact and less action on the basepaths. Strikeouts became more common than hits for the first time in 2018, and if this season’s strikeout spike and BABIP outage endure, K’s will open up a larger lead.

If this season’s BABIP were to stay at .276, it would mark the largest year-to-year decrease since baseball’s 19th-century architects were waffling about whether walks should count as hits. But more batted balls are bound to start falling. If hitters have been out of sorts, it’s likely that they’ll get their acts together as the season proceeds—and, perhaps, as they realize that ever-escalating launch angles may not work as well when the ball behaves itself. And if poor luck has contributed to this out-infested interlude, it will probably regress. “We can’t hit our way out of a paper bag right now, so any progress would be great,” the assistant GM says. If it’s any consolation, a lot of the league’s lineups are stuck inside the same bag.

Thanks to Lucas Apostoleris of Baseball Prospectus for research assistance.