Major League Baseball has somewhat cushioned its baseballs amid an increase in home runs over a number of years, a source confirmed to The Associated Press Monday.
MLB expects the changes to be subtle, and a memo to teams last week cites an independent lab that found the new balls will fly 1 to 2 feet shorter on balls hit more than 375 feet. Five other teams also plan to add humidors to their stadiums, meaning that 10 of MLB’s 30 stadiums are expected to be equipped with storage areas with controlled humidity.
A person familiar with the story spoke to The Associated Press Monday on condition of anonymity because the memo, sent by MLB executive vice president of baseball operations Morgan Sword, was sent privately. The Athletic first reported on the contents of the memo.
The composition of official Rawlings baseballs used in MLB games has come under scrutiny in recent years. A record 6,776 home runs were hit during the 2019 regular season, and home runs dropped only slightly during the pandemic-shortened 2020 season, from 6.6% of record performances resulting in home runs in 2019 to 6.5% last year year.
A four-person committee of scientists commissioned by MLB concluded after the 2019 season that baseballs had less resistance on average than in previous seasons, adding to the increased power. In their report, the increase was partially attributed to inconsistencies in the seam height.
The balls used in MLB are hand-sewn by workers at the Rawlings factory in Costa Rica, leading to inevitable minor anomalies in production that can have significant consequences.
The league requires all baseballs to have a coefficient of restitution (COR), essentially a measure of the bounce of the ball, ranging from .530 to .570, but for the past few years, the average COR has been an upward trend within specification range.
In an effort to better center the ball, Rawlings has reduced the tension on the first of three twists of yarn in the ball. His research estimates that the adjustment will reduce the COR from 0.01 to 0.02 and also reduce the weight of the ball by 2.8 grams without changing its size. The competition does not expect the weight change to affect the speed of the pitchers.
The memo did not address ball resistance, which remains a more difficult issue to master.
The Colorado Rockies, Arizona Diamondbacks, Seattle Mariners, New York Mets, and Boston Red Sox already have humidors. The five teams that added humidors were not identified in the memo.