MLB has recalibrated the baseball for 2021, and the by-product could be fewer home runs.
A memo was recently released to all teams, outlining a decrease in COR — coefficient of restitution — to the baseball, which correlates with bounciness. A higher COR means more bounciness and the faster a ball will travel off the bat.
The memo was obtained by The Athletic, which first reported the change.
“In an effort to center the ball with the specification range for COR and CCOR, Rawlings produced a number of baseballs from late 2019 through early 2020 that loosened the tension of the first wool winding,” the memo from the Commissioner’s Office read.
The Athletic projected the changes would result in 5 percent fewer home runs this season.
Normally, MLB would have instituted the change without an announcement, but decided to alert clubs in an effort to remain transparent, given the sensitivity of the topic, with increasing home-run rates.
The spec range for baseballs used by MLB is between .53 and .57. In recent seasons, the spec range has trended closer to the top end, and the reduction will bring the number closer to the middle.
A person briefed on the matter indicated Rawlings brought re-centered baseballs to MLB before the start of last season, but a decision was reached not to use them until it could be verified in a laboratory that the baseball had indeed been re-centered. The lab results meshed with Rawlings’ claim, bringing the baseballs for 2021 that MLB hopes will be more consistent.
The MLB memo included a footnote, according to The Athletic, that says an independent lab found that balls traveling more than 375 feet lost 1-2 feet of batted ball distance with the new ball.
Though higher COR is correlated with more home runs, a person briefed on the matter says MLB does not believe the decrease in range will drive a change in home run rates.