MLB Moves Check-Swing Robot Ump Challenges, Experimental Rules to Triple-A

The league will also test moving second base, reducing pitcher disengagements, and stricter limits on batter timeouts.

Mar. 16, 2026 at 5:52pm

Got story updates? Submit your updates here. ›

Major League Baseball is expanding its experiment with robot umpire technology that allows challenges to checked swing calls. The system will move from Class A to Triple-A this season. MLB will also test moving second base, reducing pitcher disengagements, and stricter limits on batter timeouts at the Triple-A level.

Why it matters

These experimental rules are part of MLB's ongoing efforts to improve pace of play, increase stolen bases, and leverage new technologies to enhance umpiring accuracy and consistency across the league.

The details

The Automated Ball-Strike Challenge System, or "robot umpire", will launch when the season starts on March 25 following tests that began in the minors in 2019. Teams will have two challenges per game, and can keep their challenge if successful. Additional challenges become available in extra innings. MLB will also test moving second base slightly to position it entirely within the infield, reducing the distance between bases. At Triple-A, the league will test lowering the number of allowed pitcher disengagements from the rubber from two to one per plate appearance, and stricter limits on batter timeouts.

  • The checked swing challenge test will expand to the Triple-A Pacific Coast League starting on May 5.
  • Umpires in the Triple-A International League will be instructed to apply the 45-degree threshold for determining swings starting May 5.

The players

Joe Martinez

MLB vice president of on-field strategy.

Got photos? Submit your photos here. ›

What they’re saying

“The batter, pitcher or catcher may also appeal the umpire's decision regarding whether the batter swung at a pitch. A swing will be considered to have occurred if the maximum angle between the bat head and the bat handle exceeds 45 degrees.”

— Joe Martinez, MLB vice president of on-field strategy

What’s next

The judge in the case will decide on Tuesday whether or not to allow Walker Reed Quinn out on bail.

The takeaway

These experimental rule changes in the minor leagues demonstrate MLB's ongoing efforts to improve pace of play, increase stolen bases, and leverage new technologies to enhance umpiring accuracy and consistency across the league.