Major League Baseball announced four new experimental playing rules on Thursday that will be in play during the 2021 MiLB season. All of the playing rules have been approved by the Competition Committee and the Playing Rules Committee.
The following playing rules will be in effect during the 2021 minor league season:
- Triple-A (Larger Bases): To reduce player injuries and collisions, the size of first, second, and third base will be increased from 15 inches square to 18 inches square. The competition committee also expects the shorter distances between bases created by increased size to have a modest impact on the success rate of stolen base attempts and the frequency with which a batter-runner reaches base on groundballs and bunt attempts.
- Double-A (Defensive Positioning): The defensive team must have a minimum of four players on the infield, each of whom must have both feet completely in front of the outer boundary of the infield dirt. Depending on the preliminary results of this experimental change, MLB may require two infielders to be positioned entirely on each side of second base in the second half of the Double-A season. These restrictions on defensive positioning are intended to increase the batting average on the balls in play.
- High-A (“Step Off” Rule): Pitchers are required to disengage the rubber prior to throwing to any base, with the penalty of a balk in the event the pitcher fails to comply. MLB implemented a similar rule in the second half of the Atlantic League season in 2019, which resulted in a significant increase in stolen base attempts and an improved success rate after adoption of the rule.
- Low-A (Pickoff Limitation, Pitch Timer, and ABS):
- ALL Low-A Leagues: Pitchers will be limited to a total of two “step offs” or “pickoffs” per plate appearance while there is at least one runner on base. A pitcher may attempt a third step off or pickoff in the same plate appearance; however, if the runner safely returns to the occupied base, the result is a balk. Depending on the preliminary results of this experimental rule change, MLB will consider reducing the limitation to a single “step off” or “pickoff” per plate appearance with at least one runner on base.
- Low-A Southeast: In addition to the limitation on step offs/pickoffs, MLB will expand testing of the Automatic Ball-Strike System (“ABS”) that began in the Atlantic League and Arizona Fall League to select Low-A Southeast games to assist home plate umpires with calling balls and strikes, ensure a consistent strike zone is called, and determine the optimal strike zone for the system.
- Low-A West: In addition to the limitation on step offs/pickoffs, following successful pace of game rules testing among Florida State League teams in 2019, on-field timers (one in the outfield, two behind home plate between the dugouts) will be implemented to enforce time limits between delivery of pitches, inning breaks and pitching changes. The on-field timer used in Low-A West will include new regulations beyond the system currently used in Triple-A and Double-A to reduce game length and improve pace of play.
The rules will be closely monitored by Major League Baseball and their impacts on the game will be analyzed throughout the season as MLB determines if they will continue to implement the rules. These rule change that are being put into play this season are in an effort to increase action on the basepaths, create more balls in play, improve the pace and length of games, and reduce player injuries. It’s also in an effort to increase entertainment on the field for the fans.
“We are listening to our fans. This effort is an important step towards bringing to life rules changes aimed at creating more action and improving the pace of play,” said Michael Hill, MLB Senior Vice President of On-Field Operations.”
MLB Senior Vice President of On-Field Operations said the rules are designed to “put more balls in play, create more excitement on the basepaths and increase the impact of speed and athleticism on the field.”
The game of baseball is always changing and evolving, and as it does, Major League Baseball attempts to provide the best version of baseball for its fans and players.

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