Baseball’s top minor leagues are switching to a challenge system full-time for their test of robot umpires.
Major League Baseball has been experimenting with the automated ball-strike system in the minor leagues since 2019. It has been used at all Triple-A ballparks this year for the second straight season, the robot alone for the first three games of each series and a human with a challenge system in the final three.
Starting June 25, only the challenge system will be used, according to a memo sent Tuesday from MLB vice president of on-field strategy Joe Martinez to farm directors and Triple-A managers that was obtained by The Associated Press.
MLB says 47% of challenges have been successful this year.
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As part of the change, the number of challenges allowed per team will be decreased from three to two in the International League but will remain at three in the Pacific Coast League. A team retains its challenge if successful, similar to the regulations for big league teams with video reviews.
Baseball Commissioner Rob Manfred said last month robot umpires were unlikely to come to the major leagues for 2025 and refinements were needed.
“There’s a growing consensus in large part based on what we’re hearing from players that the challenge form should be the form of ABS if and when we bring it to the big leagues, at least as a starting point,” Manfred said on May 23 following an owners meeting. “I think that’s a good decision.”
Coming to a consensus on what a computer strike zone should look like remains an obstacle. There is little desire to call the strike zone as defined in the rule book as a cube. The ABS currently calls strikes solely based on where the ball crosses the midpoint of the plate, 8.5 inches from the front and the back. The top of the strike zone was increased to 53.5% of batter height this year, up from 51%.
In data accompanying the memo, MLB said 61% of staff and players prefer the challenge system and 11% liked the full robot system. MLB said fans preferred the challenge system by a 2-1 margin.
MLB said almost 40% of Triple-A games have had more than six total challenges and that 89% of fans said the optimal number was six or fewer.
