MLB testing multiple experimental rule changes in minor leagues

Major League Baseball announced plans to test a variety of experimental rule changes across the minor leagues in 2021 on Thursday.

Each level of the minors will become a testing ground for at least one new rule. The changes are MLB's latest attempt to increase the number of balls in play and the pace of games.

Triple-A will feature new larger bases that are 18 square inches, up from the longtime standard of 15. It's hoped this will lead to more stolen bases and runners reaching base on ground balls. Injury concerns also prompted the change.

In Double-A, a ban on extreme defensive shifts will be tested, also in an effort to increase balls in play. The new rule will force teams to play at least four defenders on the infield with "both feet completely in front of the outer boundary of the infield dirt." This will be in effect for at least the first half of the Double-A season. Depending on the results, MLB may require clubs to play two infielders on each side of second base during the second half.

High-A leagues will adopt the "step off rule" that was previously tested in the independent Atlantic League. Pitchers will be called for a balk if they don't completely disengage from the rubber before throwing to a base. This rule is designed to increase stolen bases.

The Low-A circuits will feature several unique changes. All Low-A pitchers will be limited to two pickoff attempts per plate appearance. If a pitcher tries for a third pickoff but the runner is safe, he'll be charged with a balk.

The new Low-A Southeast League will also test an automatic strike zone system previously used in the Atlantic League and Arizona Fall League. The league is set to use additional timers to increase the pace of play as well, including between the delivery of pitches.

MLB has been working to fix numerous on-field issues following several years of rising home-run and strikeout numbers and decreasing balls in play. One new step has been taken at the MLB level this year with the introduction of slightly deadened baseballs.

Former Chicago Cubs president Theo Epstein joined the league office as an on-field issues consultant this offseason. Former Miami Marlins executive Michael Hill also joined MLB as its senior vice president of on-field operations.

The minor-league seasons will begin in May.