2021 MLB Rule Changes

WS Trophy

2019-2020 Rule Changes

 Rule changes for the 2021 season

This is the only new rule added at the big league level this year. If after a dropped third strike the umpire or batter inadvertently deflects the baseball—thereby impeding the catcher—the batter is out and runners are returned to their bases. This is a clarification to an existing rule that makes clear intent is not a consideration.

MLB reached an agreement with the players union on health and safety protocols for the 2021 season. There will be no universal DH or expanded playoffs, but doubleheaders will once again be seven innings and extra innings will begin with a runner on second base. Active rosters will return to the normal size of 26 players but teams will be permitted a five-man taxi squad for home games and up to 28 players at either their alternate training sites or Triple-A affiliate. MLB also reserves the right to require neutral sites for postseason games if deemed necessary.

Following the lead of the NFL and NBA, all players, coaches and essential personnel will be required to wear contact tracing devices at all times. All covered individuals will be tested at least every other day, while their household members will be provided with testing throughout the season as well. Fans weren’t permitted in stadiums last year but are expected to be allowed to attend games in limited capacity depending on local restrictions in each individual market.

In addition, reacting to changes in ball flight over the past few years, a committee of scientific experts recommended narrowing the gap in the specifications of the official baseball (i.e., size, weight, coefficient of restitution, or COR). Many of the baseballs were playing to the “hotter” end of that gap. This year the baseballs are designed for a COR in the middle of the narrower spec gap—essentially eliminating baseballs at the “hot” end of the old gap. MLB says Rawlings achieved that goal by loosening the tension of the first wool winding. 2020 balls were used almost exclusively in spring training, so we haven't seen the effect yet.

Point of interest: MLB began to arrange plans last year for umpires to announce results of replay changes with NFL-style explanations over public address systems, but COVID-19 wiped out those plans. Umpires are on board and the plans are still in place, but COVID-19 protocols still are delaying the rollout. You might see such announcements in time for postseason play this year. If not, it should be a go in 2022.

2018 Rule Changes / 2017 Rule Changes / 2016 Rule Changes / 2015 Rule Changes  / 2014 Rule Changes

Page back

All rules © MLB. All rights reserved.