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MLB will experiment with new rules in minors in 2021

A new rule for each level, to in the darkness bind them

Texas Rangers v Oakland Athletics

Major League Baseball has done a lot of tinkering with the rules over the last several years, and that trend will continue in 2021 with a new round of experiments in the minor leagues.

The Triple-A, Double-A, and High-A levels will each adopt a different change when they begin their seasons in May, and the Low-A level will try out multiple ideas. The league’s press release cites goals including increases in balls in play and action on the basepaths, improved pace, and a reduction in injuries.

These are just the latest new concepts to be tossed around in baseball. In recent summers we’ve seen pitch clocks, limits on mound visits, automatic intentional walks, a three-batter minimum, and a 26th roster spot. Last year brought emergency measures due to the coronavirus pandemic, including a universal DH, seven-inning doubleheader games, and a free runner on second base in extra innings, all of which were already established in the minors before their temporary adoption in the majors.

The new rules are detailed below, with most text copied directly from the MLB press release.

  • 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 rule 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 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, all leagues (Pickoff Limitation): 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 (Robot strike zone): In addition to the limitations 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 (Pitch timers): In addition to the limitations 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 the pace of play.

MLB insider Anthony Castrovince offers more details and background.


Hot takes: The bigger base thing will probably look weird at first, but doesn’t bother me, especially as a safety measure. But the shift reduction, step-off rule, and pickoff limits could have massive impacts on gameplay. Perhaps we’d all end up liking the results, because it could mean more hits/steals and less Three True Outcomes slugball, but we’ll see what consequences come from chasing those desired goals so aggressively. Also, we’ll finally see the beginning of robot umps for balls and strikes.

If this is truly an honest test of ideas, and not a slow rollout of an inevitable future that’s already been decided, then why not? The minors are for trying out new players, may as well try out new rules too, even if all of us can surely find at least one proposal on that list that we loathe.

And for what it’s worth, Matt Olson probably wouldn’t mind curtailing defensive shifts.