MLB's New Rule Change Experiments Revealed Ahead of 2026 Season

MLB has already added a new wrinkle for the 2026 season with the Automated Ball-Strike Challenge System (ABS), and the league is reportedly testing out even more potential changes.

According to the Associated Press, MLB is moving its experiment of allowing challenges to checked swing calls under a robot umpire technology system from Class A to Triple-A.

Under the current ABS, ball/strike calls by the human umpires can be appealed, with each team having two challenges and keeping its challenge if successful. The league began experimenting with challenges on checked swing calls in the Class A Florida State League last May before extending the test to the Arizona Fall League. This year's checked swing experiment will expand to the Triple-A Pacific Coast League in addition to the FSL, starting on May 5.

"The batter, pitcher or catcher may also appeal the umpire's decision regarding whether the batter swung at a pitch," according to the memo from MLB vice president of on-field strategy Joe Martinez to general managers and other club executives. "A swing will be considered to have occurred if the maximum angle between the bat head and the bat handle exceeds 45 degrees."

The memo also reportedly revealed that the league "will also test moving second base slightly to position it entirely within the infield, which would reduce by 9 inches the distance between first and second, and between second and third." It will also experiment with "reducing permissible disengagements by pitchers from two to one per plate appearance and stricter limits on batter timeouts and resetting the pitch clock for issues with PitchCom, the electronic signaling device that has been used since 2023."

In a change unlikely to reach the majors, the league will test allowing starting pitchers to re-enter games. This experiment is expected to stay "in the lowest level of the minor leagues" as a way to "improve development and player health by allowing more flexible workload management."

MLB is continuing to find new ways to modernize the sport of baseball, so it will be interesting to see if any of these experiments lead to changes at the major-league level.