Major League Baseball announced Tuesday that it will experiment with a pair of new rules during the 2021 Atlantic League season: a “double-hook” implementation of the designated hitter and moving the pitching rubber back one foot. MLB and the Atlantic League began a partnership back in 2019 wherein the latter would serve as a testing ground for rule changes and pace-of-play alterations.

The “double-hook” designated hitter rule will be in place for the entirety of the 2021 Atlantic League season. Under the new rule, a team will lose its designated hitter once the starting pitcher is pulled from the game. From that point forth, the team will need to either deploy a pinch-hitter or allow a relief pitcher to bat in what was the designated hitter’s place.

The goal of the rule, per the league, is to “incentivize teams to leave their starting pitchers in longer, increase the value of starters who can work deeper into games and increase the strategic element in the late innings of a game.”

Turning to the pitching rubber experiment, that change will only be implemented in the second half of the Atlantic League season. (The first-half data will then be compared to second-half data as a direct point of comparison.) MLB’s release notes that the average fastball velocity has risen from 91.6 mph in 2010 to 93.3 mph in 2021. The league posits that a hitter’s reaction time on a 93.3 mph pitch thrown from 61 feet, six inches is approximately the same as the reaction time on a 91.6 mph pitch thrown from 60 feet, six inches.

Within its release, MLB indicates that their analysis concluded a one-foot increase “would be the minimum interval needed to evaluate a change in mound distance,” adding that the change is “expected to be meaningful without being disruptive.” The goal, as readers have surely deduced, is to curb the league’s rising strikeout rate and increase the number of balls in play.

MLB feels the change has been sufficiently determined to be safe and free of increased injury risk, citing a 2019 study conducted by the American Sports Medicine Institute. Within that study, the ASMI asked collegiate pitchers to throw from 60’6″, 62’6″ and 63’8″, ultimately concluding that there were “no significant differences in key measures of rotational motion (kinetics) or acceleration (kinematics).” Pitch velocity and strike percentage also remained consistent, per that study.’s Anthony Castrovince also raises an interesting point on the potential shift in distance from home plate to the pitching rubber, writing that league study found a standard deviation of seven inches for how catchers set up behind the plate. Catcher positioning varies on a player-to-player basis, with the difference between some catchers being as large as three feet.

It’s worth emphasizing, of course, that the experimentation in the Atlantic League does not necessarily indicate that either of these changes is any sort of lock to be added to Major League Baseball’s official rulebook moving forward. For instance, the Atlantic League experimented with a two-foot increase in distance between home plate and the pitching rubber during the second half of the 2019 season. They’ve also tested out TrackMan-assisted home plate umpires, measures to limit infield shifts, increased base sizes and the elimination of mound visits for any reason other than pitching changes. Some of those experiments have now been implemented at various minor-league levels, and that would surely be the next step for either of the measures announced Wednesday.