Major League Baseball will alter the baseball slightly in 2021, though changes to the ball will be subtle.
According to the Associated Press, a memo sent to all 30 clubs last week cited an independent lab that found the new balls will fly one to two feet shorter on balls hit over 375 feet.
After the league saw a record 6,776 homers hit in 2019 (the last 162-game season that was played), the home run rate fell from 6.6% of plate appearances in '19 to 6.5% during the pandemic-shortened '20 campaign.
Following the 2019 season, a committee of scientists commissioned by MLB came to the determination that the baseballs had less drag on average than in previous seasons, one of the reasons for the boost in home runs. The key to the boom? Inconsistencies in seam height.
MLB’s balls are hand-sewn by workers at the Rawlings factory in Costa Rica, which can result in minor deviations in production. The league requires all baseballs to have a coefficient of restitution (COR) -- in simple terms, the bounciness of the ball -- ranging from .530 to .570, but the average COR had trended toward the top of that range in recent years.
Rawlings has loosened the tension on the first of three wool windings within the ball. The company’s research believes this adjustment will bring the COR down slightly, while also lessening the ball’s weight by 2.8 grams without changing its size. According to the AP, MLB does not anticipate the weight change to impact pitchers’ velocity.
MLB’s memo did not mention anything about the drag of the new balls.
The AP also reported that the number of teams using humidors to store baseballs will double from five to 10 this season, keeping the balls in humidity-controlled storage areas. The Rockies, D-backs, Mariners, Mets and Red Sox already have humidors in their respective ballparks.