February 16, 2021

MLB Plans "Minor Changes" To Baseballs In 2021 "To Reduce Offense Slightly"

MLB is messing with the baseball again. But this time, they are admitting it.

Eno Sarris and Ken Rosenthal of The Athletic reported last week on an internal memo MLB sent on February 5 to "general managers, assistant general managers, and equipment managers outlining minor changes that might combine to reduce offense slightly in the 2021 season".

Sarris and Rosenthal:

Research conducted by Rawlings says the balls will be centered more in the midpoint of the established COR range, which is from .530 to .570 with a midpoint around .550, as the first report on the home run rate surge stated. So the COR likely changed around .01 to .02 at most, and the ball mass was likely reduced by less than 2.8 grams. That might seem like no big deal, until you compare this situation to what happened in Korea when the Korean Baseball Organization deadened the ball there. 

[*: "COR is the coefficient of restitution, or the relationship of the incoming speed to the outgoing speed. So, in other words, this new ball will be less bouncy."]

On the field, Korean baseball was drastically different from one year to the next: Slugging in KBO was down 14 percent and homers were cut by a third. That happened after the KBO changed the ball size by one gram and moved the COR by .01 to .02 (from a midpoint at .4254 to one at .4134). So with changes of the same magnitude as those being implemented by MLB this offseason, the game in Korea changed dramatically from one season to the next. . . .

The MLB memo includes a footnote that says an independent lab found that fly balls that went over 375 feet lost one to two feet of batted ball distance with the new ball. That also sounds like no big deal, but every 3.3 feet of distance increases the likelihood of a home run by ten percent. An analyst familiar with the physics and math of this situation said the relationship was linear enough to estimate that this change will reduce home run rates by around five percent. 

"It'll be like adding five feet of outfield walls to every wall in the big leagues," the analyst said. But it's hard to know the specifics without knowing what the drag difference will be. The memo mentions nothing about the drag, which has been a major factor in differences in how the ball has performed in the last few years. Drag is more difficult to control than bounciness, one source said. Others felt the drag difference would be negligible. 

Reaction within the league's front offices and coaching ranks was mixed. 

"It sounds to me as it will result in more ball consistency and a very, very slight deadening of the ball," said one general manager, referencing the memo's language about placing the ball in the middle of the 'specification range.' 

When asked if it seemed baseball was deadening the ball on purpose, one general manager agreed: "That's the desired result." . . .

With strikeouts in the game surging, one risk in deadening the ball is that it will leave the game with all those swings and misses and fewer big flies. But a five percent reduction in homers won't bring us back to before the live ball era; it's more likely the ball will fly like it did in 2017, a season that broke home run records before 2019 made mincemeat of those home run records. . . .

The addition of five more [unidentified, as of now] teams using humidors, bringing the total number to 10, also might impact offense. The Mariners, Mets, Red Sox, and Rockies already store their balls in humidors. So do the Diamondbacks . . .

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