Tuesday, May 24, 2022

MLB home runs are way down so far in 2022; here’s how the league’s recent tinkering deadened the baseball

Tuesday night at Dodger Stadium, Dodgers center fielder Cody Bellinger laid into a center-cut 94 mph fastball from Giants righty John Brebbia. The pitch jumped off the 2019 NL MVP’s bat at 102.3 mph and sailed toward center field … and then it just died. Mauricio Dubón made the catch with relative ease a few steps in front of the wall. 

“Gimme a break,” Dodgers broadcaster Joe Davis said.

“It’s the ball,” Duane Kuiper quipped on the Giants broadcast.

“I thought Bellinger’s ball was out,” Dubón told Evan Webeck of the Bay Area News Group after the game. “Then it looked like it hit a wall. I was getting ready to jump, and it just died at the end.”

Bellinger’s drive looked gone off the bat because the last few seasons have conditioned us to expect balls hit like that to carry over the wall for a home run. This year, these well-struck balls are more frequently coming up short, and settling into outfielders’ gloves. Home runs are down early in 2022 and not by a tiny little bit either. Teams are averaging 0.90 homers per game, down from 1.22 last year and 1.39 in 2019, the year MLB set all sorts of home run records

Suffice it to say, MLB‘s recent history is rife with inconsistency when it comes to the properties of the actual, physical baseball itself. This has resulted in a great deal of unpredictability from year to year, especially when it comes to home run rates. 

Now let’s undertake a brief chronicling of how the ball has changed over the last half-decade-plus or so, which will set the scene for a deep dive into the 2022 season thus far. 

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2015

In 2014, MLB teams averaged 0.86 home runs per game, but in 2015 that figure vaulted to 1.01 per team, per game. So what happened? ESPN Sport Science obtained a sample of baseballs used from 2014-15 and another of balls used from 2016-17 and, with an assist from the USC School of Medicine, ran them through a CT scan. They found that the 2016-17 baseballs had a significantly less dense cork-and-rubber core than the earlier baseballs. A subsequent analysis by Kent State University researchers discovered that the newer baseballs had slightly more silicon in the core than the older sample. The baseballs became a bit bouncier, and a lower seam height meant less resistance as the baseballs traveled through the air. All those factors combined made the baseball much livelier. This “juiced” ball probably landed in the hands of MLB pitchers in the second half of the 2015 season, which explains the overall increase in home run rate for 2015. That rate ticked up to 1.16 in 2016 and 1.26 in 2017 and then eased back down to 1.15 in 2018. 

All of this prompted MLB commissioner Rob Manfred in August 2017 to bring together various experts in the fields of physics and quantitative analysis to try to find out what was going on. The committee focused its efforts on studying the physical properties of the baseball, weather and climate conditions, and player behavior. In addition to using Statcast data and conducting controlled experiments involving 180 unused official baseballs that dated from 2013 to 2017, the committee also inspected Rawlings’ production plant in Costa Rica. In broad terms, the committee found that baseballs were experiencing less drag in the air, which allowed them to travel farther, but they couldn’t pin down a reason for the change. The report indicated that the “pill” of the baseball, or the core, may have been better centered during manufacturing than it was in years past. That improved symmetry may have helped the ball carry farther. 

Then, however, 2019 happened. 

2019

For the 2019 season, teams averaged a record 1.39 home runs per game, which in turn yielded a record tally of 6,776 home runs for the year. Perhaps prompted by an outcry among pitchers, MLB undertook another fact-finding mission centered on the baseball itself. The report, released in December 2019 and authored by a committee of four scientists, concluded: 

“Analysis of StatCast data shows that the increase in home run rate between 2018 and 2019 was due in part to a change in launch conditions and in part to a change in the baseball drag. The increase due to changes in launch conditions was determined to be due to a change in player behavior rather than to changes in the baseball. … The laboratory experiments, using newly developed techniques, show a correlation between drag and seam height, with the average seam height in 2019 smaller than that in 2018 by less than 0.001 inches.”

Specifically, the committee found that roughly 40 percent of the increase in power was due to a widespread “change in player behavior,” which refers to increasing emphasis of hitters on achieving a launch angle off the bat that’s ideal for power production. The rest, they posited, was due to seam height.

That, however, was not the final word. Astrophysicist Dr. Meredith Wills, who has emerged as the leading independent authority on the state of the baseball, conducted her own examination of the 2019 baseball relative to earlier models and presented her findings in a June 2019 piece for The Athletic. She hypothesized that Rawlings, starting with the 2019 batch, began machine drying the baseballs whereas before they allowed baseballs to air dry. That, in turn, perhaps allowed Rawlings to better meet MLB’s increased demand for baseballs (Triple-A used MLB baseballs in 2019, and, just as in MLB, home run rates vaulted). The physical changes she found in the baseballs starting in 2019 are consistent with what would happen if you applied heat to a baseball to speed up the drying process. Dr. Willis’ findings didn’t exactly align with those of the MLB-assembled panel while at the same time reinforcing the fact that the ball changed prior to the 2019 season. 

The 2019 postseason

Then something happened between the latter weeks of the regular season and the start of the 2019 playoffs. The power numbers during the playoffs dropped so dramatically that something beyond just small sample size noise almost had to be at work. Indeed, the Cardinals‘ front office found that during the LDS round, balls were carrying about 4.5 fewer feet than balls of a similar contact quality were during the regular season. 

So what happened? That December 2019 report commissioned by MLB stated that drag — or how the air works against a baseball flying through it — increased in the postseason but that a reason for that wasn’t exactly clear. Dr. Willis, though, found a reason. As she wrote for The Athletic, MLB very likely ran out of 2019 regular-season balls — thanks to increased in-game usage plus additional authenticating of game balls for memorabilia sales, in addition to using MLB balls at the Triple-A level in 2019 — which meant that the league had to use some older balls during the 2019 postseason. Those older balls weren’t as “juiced” as the 2019 regular-season batches. 

2020 and 2021 

Over the past two seasons, the first of which was heavily abbreviated because of COVID, the ball was still pretty lively in terms of home run rates, albeit not quite to the extremes of the 2019 regular season. This is likely the result of tweaked manufacturing processes by Rawlings (which is owned by MLB) designed to produce a more consistent ball that resides at or near the midpoint of specifications. As well, the gradual increase in the number of teams storing baseballs in a humidor also likely contributed to the modest “deadening” effect. 

Going into the 2021 season, MLB told teams they could expect a less lively ball for that year. However, Bradford William Davis of Business Insider reported in November of last year that Dr. Willis discovered the use of two different types of baseballs in 2021. One was the lighter ball designed to carry less and the other was a batch of heavier, livelier balls. MLB blamed supply-chain disruption caused by the pandemic for the mixing of batches. Whatever the reasons, it was a frustrating dynamic for pitchers and batters alike. 

All of that chaos set the stage for the state of the baseball in 2022. 

2022

MLB wants more contact and more balls in play, and more action on the field in general. The thinking is that, by deadening the ball and making home runs harder to hit, batters will instead focus on contact. Sensible. The only problem is that adjustment can’t be made overnight, and now a bunch of would-be homers are becoming fly outs, and offense is down around the league. Teams are averaging 4.04 runs per game in 2022. Scoring hasn’t been that low in a full season since 1980 (4.00 runs per game).

Rob Arthur has meticulously tracked the baseball’s drag over the years — drag is a component that determines how much the air slows the ball down in-flight — and found the drag on the 2022 baseball is way up. From Arthur:

Through about two weeks so far this season, it appears we are on track for a high-drag, and thus low-homer, year. That dovetails nicely with other studies on the topic that are finding home run rates quite reduced, even adjusting for the weather, as well as other investigations of the baseball and home run rates by two researchers helping MLB study the topic, Alan Nathan and Jim Albert. In raw (non-weather-adjusted) terms, we are seeing the lowest rate of balls leaving the park since 2014, though that will creep up as the summer brings warmer, less dense air for the smashed baseballs to travel through. 

This is best shown with barrels. A barrel is essentially the best possible contact in terms of exit velocity and launch angle. They’re batted balls that produce a batting average north of .500 and a slugging percentage of at least 1.500, and they often come in way higher than that. Here are the MLB averages on barrels in the Statcast era (2015 to present). 

2015

102.6 mph

27.9º

400 ft

2.948

2016

102.7 mph

27.9º

400 ft

2.935

2017

102.7 mph

27.8º

402 ft

3.111

2018

102.8 mph

27.9º

397 ft

2.901

2019

102.9 mph

27.9º

401 ft

3.152

2020

103.0 mph

27.9º

403 ft

3.161

2021

103.4 mph

27.9º

400 ft

2.952

2022

103.3 mph

27.9º

394 ft

2.492

The exit velocity keeps going up (because batters are hitting the ball harder with each passing the year the same way pitchers keep throwing harder) and the launch angle has held steady, yet the average distance on barrels has dropped six feet this year. Six feet! Do you know how much six feet is? Six feet is the difference between Bellinger’s rocket being a home run and an out.

On this specific subset of batted balls — there are thousands of barrels around the league each year, so it’s not a small sample — batters are hitting the ball harder than ever and at the same launch angle, yet the ball is not traveling as far. Changes to the baseball itself are the most straightforward explanation, though it should be noted they’re not the only possible explanation.

For the first time MLB is storing baseballs in humidors at all 30 ballparks this season. Last year 10 teams used the humidor in their home ballpark: the Astros, Blue Jays, Cardinals, Diamondbacks, Mariners, Marlins, Mets, Rangers, Red Sox, and Rockies. Now all 30 clubs have a humidor, and the humidor brings the ball to average humidity. It dries out the ball in humid climates and “wets” it in dry climates. The drier the baseball, the more it flies.

Using the humidor in all 30 parks brings consistency to the baseball, at least in theory. There are so many variables in play that are impossible to quantify. How the ball is transported from the Rawlings factory in Costa Rica to each MLB city, how long the ball is stored in the humidor, and all sorts of other stuff matters quite a bit. Every time a baseball warms up and cools down, its physical properties change. Everything in the ball (the leather, the cork, etc.) experiences wear and tear, for lack of a better term.

The humidor has the most impact in extreme climates like swampy Florida (even in a dome) or the Arizona desert, but it can make some amount of difference everywhere. The 10 ballparks that used the humidor last season function as a control group. Here are the home runs per ball in play numbers:

2021 HR/BIP

4.5%

5.1%

2022 HR/BIP

3.8%

3.5%

The home run rate in the 10 parks that used the humidor in 2021 is down 0.7 percentage points. It’s down 1.6 percentage points in the other 20 parks, the parks that did not have humidor in 2021 but do have one in 2022. If we say the 0.7 percentage point decline is a result of the ball being changed, then the other 0.9 percentage points are the result of the humidor.

It’s not quite that simple, of course, but clearly the humidor is having some affect on home runs. And that affect may change. It is only May 5. The weather will warm up in the coming weeks and soon it will be stick-to-your-seat humid in many MLB cities. The ball will behave differently because the climate will be different, so the humidor will change the properties of the baseball even more.

Last year MLB said the “2022 season will be played with only balls manufactured after the production change,” meaning the deadened ball we were supposed to get in 2021. That appears to have happened. An additional 20 teams are using a humidor now, and while the humidor doesn’t automatically lower the home run rate (it could raise it in some climates), it is more likely to lower it given the fact baseball is largely played outdoors in the summer.

Bottom line, the baseball is not carrying the same way it did the past few years. The home run rate is down significantly early in the season, and because hitters have yet to adjust, offense is way down too. The season is still young and we need a lot more data before we have a full understanding of how this baseball works and the humidor’s impact. The early returns suggest a return to 2013 and 2014, the last time teams averaged fewer than a home run per game, and offense was this low league-wide.

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