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MLB intended to deaden the 2021 baseball but Spring Training data indicates HR rates are up

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Prepare for a lot of unintended consequences

Allan Henry-USA TODAY Sports

Since 2015 something funky has been going on with the physical baseball. In February, after multiple years and two official reports, MLB finally announced it would deaden the baseball for 2021. It should not be lost on anyone that the memo announcing that change was leaked mere hours before Sports Illustrated’s Stephanie Apstein and long-time baseball sleuth Dr. Meredith Wills dropped their report on the baseball deciphering the batch codes which included the first admission from MLB that they had already been manipulating the ball (emphasis mine):

SI first asked MLB last week about its manipulation of baseballs. After the league admitted to SI that it had made adjustments, but insisted that they were minimal, it sent a memo to general managers, assistant general managers and equipment managers informing them of the changes.

This is the first time MLB has publicly acknowledged experimenting with the ball, indicative of its typically close-to-the-vest approach.

Like many fans I expected we’d see more long fly outs, fewer home runs, and home runs that traveled less impressive distances than before. If you’ve been watching Cubs Spring Training you know that home runs are not declining. I mean look at this shot from Jake Marisnick [VIDEO].

Jake Marisnick has hit 56 home runs in eight years in the major leagues. He’s not exactly a power guy but this spring he hit four home runs in 22 at bats.

It turns out Marisnick wasn’t the only batter with a bit more demonstrated oomph this Spring. The Ringer published this piece from Ben Lindbergh and data scientist Rob Arthur the day before Opening Day and honestly I am just laughing at this point (emphasis mine).

HR per batted ball event - spring and regular season by year
The Ringer

The first important takeaway is that while spring-training home run rates on contact are generally a little lower than the corresponding regular-season rates—likely because of differences in quality of competition, weather, and other factors—the two rates tend to track each other closely: As regular-season home run rates have soared, spring-training rates have tended to follow (or lead). The correlation between the two over the past 15 years is .91, where 0 indicates no connection and 1 represents rates in perfect lockstep. The second takeaway is that the HR/Contact rate this spring is higher than it has been in any other spring on record. Spring dingers aren’t down; they’ve reached a record level, topping 5 percent of non-sacrifice batted balls. And in six out of the past seven seasons, the regular-season rate has moved in the same direction that the spring-training rate did.

The piece goes on to acknowledge that there were likely a mix of 2020 and 2021 balls in Spring Training batches and to demonstrate that balls have different drag effects this spring. However, and this is really the crux of the issue, apparently the balls with higher drag are resulting in more home runs and more pitch movement - which is kind of the opposite of what MLB told us they planned:

All else being equal—there’s that phrase again—higher drag should translate to less carry and fewer home runs. Yet the higher-drag balls also have a higher home run rate on contact, because they have a substantially higher average exit speed (by about 0.8 miles per hour). That’s the opposite of what we would expect to see if their COR and CCOR were really reduced, though Jeff Kensrud of the Washington State University Sports Science Laboratory cautions that those traits are dependent on temperature, moisture content, and how the balls are being stored. (Ten teams will use humidors this year during the regular season, up from five last year, but teams haven’t used humidors in spring training.)

The higher-drag balls also seem to move more: Fastballs gain an extra 0.45 inches of vertical movement, and curveballs add 0.3 inches, relative to the lower-drag balls. In possibly related news, the higher-drag balls have a higher whiff-per-swing rate, by almost 3 percentage points. None of these findings conflicts with what Snell and Cole said: A difference in seams could account for improved grips, greater comfort, and more movement, as well as elevated drag, which could cause balls to carry less but possibly still fly farther if they’re leaping off the bat at higher speeds.

You really should check out the whole piece because it also contains incredible information like the fact that MLB plugged their changes into an equation but didn’t actually test the new ball in a laboratory. I cannot even begin to fathom all of the potential unintended consequences that could have this season.

So, to sum it up: MLB announced they were deadening the ball, Spring Training used at least some of the new balls and the 2021 Spring Training home run rates set a new record for home runs per batted ball event.

It seems like while it may have been MLB’s intention to deaden the ball for 2021 their tinkering may not have resulted in the outcome they were looking for. This isn’t surprising in the slightest, but if the new ball does fly further and move more we could be in for another season of record strikeouts and home runs across the league. It’s almost as if MLB keeps manipulating the ball without a good understanding of the impact those changes will have on the game. As one MLB team front office employee said in the Ringer piece: “MLB is going to MLB.”

The Cubs set a new team record for home runs in 2019 when they hit 256 home runs. They bested the previous 2004 record of 235 on September 14 and were just padding the new record for the final two weeks of the most recent full baseball season. They were not alone. Twelve other teams set their franchise home run records in 2019. As I wrote at the time, the Cubs demolished their old record despite the fact that Wrigley Field was one of the least friendly ballparks for home runs in 2019 and despite the fact that the 2019 Cubs were a much better team at home than they were on the road. It will be worth keeping an eye on home run numbers this season, because if this Spring Training data holds true for the 2021 season the Cubs still have enough power up and down the lineup to threaten that 2019 record.