Since mid-2015, MLB’s game-used baseballs have come off the bat as if shot out of a cannon, as a more aerodynamic ball with a better-centered core has led to record leaguewide home run totals. It’s been empirically proved that both the ball and the resulting run environment have changed, but the league has been cagey about the cause. That’s understandable from its perspective, as MLB owns ball manufacturer Rawlings: A substantial change to the baseball would imply either an inability to ensure a consistent equipment-manufacturing process or a deliberate decision to change the conditions of the game without telling anyone.
Whatever the cause, the juiced ball is the most impactful and controversial equipment change in recent baseball history. But just as suddenly and inexplicably as it arrived on the scene, the juiced ball appears to have disappeared in the past few weeks.
Anecdotally, pop flies that carried over the fence for the past few years have begun to die at the warning track. Rob Arthur of Baseball Prospectus compared the drag coefficient of the baseball after the division series to the last week of the regular season and found the largest week-to-week change this season by far, and a ball that grabbed the air more than it had at any point since 2016. Given park effect, launch angle, and exit velocity, Arthur calculated that there should have been 67 home runs hit in the divisional round, when in reality there were only 43. Included in the missing 24 were three balls that would have had a 95 percent chance or better of reaching the seats in the regular season. And while the cold weather of October is an obvious place to look for an explanation, Arthur pointed out that at the time he performed his study, the average 2019 postseason game had actually been played in warmer conditions than the average 2019 regular-season game.
Over the weekend, Cardinals manager Mike Shildt said his analytics team had told him the ball was carrying 4 1/2 feet less than it had during the regular season. Maybe this is a blip, an odd batch of baseballs that just happened to come off the assembly line right when the calendar turned to October, and the ball will start jumping out of the yard again next April. But if it’s not, and the ball switches back to its pre-2015 standard without any other piece of equipment or tactical norm in the sport changing along with it, we could be in for a new dead-ball era.
The 2019 season was the 119th since the American League was founded in 1901. Out of those 119 seasons, 2019 ranked 98th highest in leaguewide batting average (.252), 91st highest in hits per team game (8.65), tied for 77th in OBP (.323), and first in strikeouts (8.81 per team game). For the second straight year—and only the second time in MLB history—there were more strikeouts than hits.
Despite this, scoring was fairly robust, with 4.83 runs per team game, which puts 2019 at 20th on the list of highest-scoring seasons. In 2019, only 46 of 135 qualified hitters hit .284 or better; in the 1921 season, the league as a whole batted .291, with an OBP 25 points higher than it is today, and scored fewer runs per game.
Against this tide of pitcher-friendly trends, there is one force, and only one, holding up today’s above-average run-scoring environment: the juiced ball, which has goosed the home run rate to such a risibly elevated level that it’s kept back the flood, like the little boy with his finger in the dike.
The most celebrated example of this home-run-reliant offensive environment is how opponents scored runs off Justin Verlander. In 2012, Verlander finished a close second in Cy Young voting when he posted a 2.64 ERA with a K/9 ratio of 9.0, a BB/9 ratio of 2.3, and an HR/9 ratio of 0.7. In 2019, Verlander posted a nearly identical ERA, 2.58, but struck out 12.1 batters per nine innings, walked just 1.7, and allowed 1.5 home runs per nine innings. Verlander allowed 66 runs, 45 of them on home runs: 28 solo dingers, seven two-run shots, and a three-run blast.
Leaguewide, the 6,776 regular-season home runs hit this year accounted for 10,617 runs, or over 45 percent of the total runs scored. The last full year before the juiced ball, 2014, teams hit 0.86 home runs per game and accounted for 33.4 percent of total runs. In the past five seasons, the number of home runs per game has increased by almost 62 percent. If the baseball suddenly reverted to its 2014 form, the consequences would be wide ranging, as fastball velocity would take a tick backward—the same forces that increase drag on a batted fly ball would increase drag on a pitched fastball. That said, 2014 was a record year at the time for both fastball velocity and strikeouts, so the effect on pitchers would be less than on hitters. And the instant teams and players realized the ball was different, they’d tweak their approaches to suit the new reality. Those competing in this year’s postseason may have done so already.
Here’s a quick and dirty estimate of what would happen if the ball remained unjuiced at the start of the 2020 regular season, but everything else about the game remained unchanged from 2019.
In the 2019 regular season, there were 44,281 fly balls hit, according to FanGraphs, of which 14.7 percent, or 6,509, became home runs. (The other 200-odd home runs were some combination of other batted ball types, mostly line drives off the bat of Christian Yelich.) In 2014, only 9.2 percent of fly balls (4,051 out of 44,028) left the yard.
Reducing the leaguewide home run rate to 2014 levels would keep 2,428 home runs in the yard. Given the 2019 leaguewide fly ball BABIP of .118, only about one in nine of those would fall in for a hit, which would turn 2,141 home runs into outs. Given the current distribution of hits per fly ball in play, there would be 80 more singles, 180 more doubles, and 26 more triples out of those 2,000-odd extra balls in play.
Changing those 2,428 home runs to a proportionate variety of outs and hits, while keeping everything else the same—plate appearances, walks, strikeouts—drops the leaguewide triple slash line from .252/.323/.435 to .239/.312/.380. That would be the lowest leaguewide SLG since 1993, the lowest OBP since 1972—the year before the DH was implemented—and the second-lowest batting average of the American League era, eclipsing only the famous second dead-ball season of 1968, in which Carl Yastrzemski won the AL batting title by hitting .301, Denny McLain won 31 games, and Bob Gibson posted a 1.12 ERA and 13 complete-game shutouts.
We might already be seeing a new wave of exceptional pitching performances with the re-deadened ball this postseason. Since the beginning of the playoffs through the first two games of both league championship series, there have been 12 individual starts with a game score of 70 or better, encompassing everything from scoreless six-inning, one-hit starts by Masahiro Tanaka and Walker Buehler to Gerrit Cole’s pair of ALDS gems to Adam Wainwright’s 120-pitch start in Game 3 of the NLDS. And that’s only through 25 postseason games; there could be as many as 16 more by the time all is said and done. For contrast, there haven’t been more than 12 starts with a game score of 70 or better in any postseason since 2013.
Looking at what Cole or Stephen Strasburg has done so far this season, it’s hard not to think of Madison Bumgarner’s dominant 2014 postseason, but this might not just be one hot month from a great pitcher, it could be partially the result of a new, unexpected, and batter-hostile environment of play. In all likelihood, no starter is going to post a 1.12 ERA next year, but with every no-doubt homer that dies on the warning track, it gets easier to imagine someone like Cole or Strasburg coming close.