What is MLB’s ‘ABS Challenge System’? Inside baseball’s newest ‘robot umps’ technology
We’re about to see something new as the Kansas City Royals open their spring training schedule with games against fellow Major League Baseball teams.
On Thursday, MLB rolled out its new “Automated Ball-Strike (ABS) Challenge System” during a Cactus League matchup between the Chicago Cubs and Los Angeles Dodgers.
Employing ABS — referred to by some as “robot umps” — is an innovative step for baseball. MLB is testing the technology at 13 spring training ballparks across Arizona and Florida — including KC’s spring home at Surprise Stadium — in coming weeks.
ABS will not reach the big leagues in 2025. Instead, it will be used during the regular season in the minor leagues for another year as league officials tweak and evaluate the still-new tech.
The Royals will get their first experience with the ABS Challenge System on Friday as they make their Cactus League debut against the Texas Rangers at Surprise Stadium (2:05 p.m. Central Time).
So what exactly does the ABS Challenge System entail? It’s an aid in calling balls and strikes.
Each team will have two ABS challenges to start a game. Only the pitcher, catcher or batter can request a challenge. A challenge is requested when one of those players taps his head and verbally asks for a review. No assistance from the dugout is allowed.
And the challenge must be made immediately after the umpire’s call. Wait too long and the chance to challenge is gone.
Once a challenge is logged, a video animation will appear on the scoreboard. Similar to tennis, an automated decision will be made nearly instantaneously. A ball or strike will be awarded following the review.
A successful challenge (call is overturned) allows a team to retain its challenge allotment. This is beneficial for other calls the team might want to dispute later in the game.
An unsuccessful challenge (call is confirmed) will cause a team to lose a challenge for the remainder of the matchup.
ABS has been used in the minors since 2021. Now, more than 60% of spring training games will be played with it.
Most Royals will be learning the ABS system from square one this season. But some of their minor-leaguers have already used it.
“In the beginning, it was tough because it was all ABS,” said Royals utilityman Nick Loftin, who experienced ABS in the minors. “There was no challenge system with it. It took the art of catching out as everything was pretty true about it.
“Top of the (strike) zone kind of disappeared. From what I noticed, even with the challenge system, I think the biggest thing is it’s pretty true on the corners. But up and down, it can kind of favor one way or another.”
Major League Baseball’s dimensions for the ABS strike zone feature a width of 17 inches — the width of home plate. But the top and bottom of the zone vary by player height.
The strike zone is centered on home plate, 8.5 inches from the front and back. If any part of the baseball touches the strike zone, it will be called a strike. A ball must be outside the zone for it to be ruled a ball, per MLB rules.
“The bottom was pretty true and, for me, the bottom was true,” Loftin said. “Corners are pretty true as well.”
Loftin said the top of the strike zone was difficult to judge. He said major-league umpires operate with a round visualization of the strike zone. Pitches higher in the zone often require the ump to make a decision — ball or strike.
The ABS Challenge System has a rigid top of the strike zone. So any pitch that is borderline could spark some confusion about whether it was a ball or strike.
Loftin believes this is something that players will have to adjust to this spring.
“Long term, if they are going to keep ABS, they need to bring it to the big leagues because the pitches I took in Triple-A are balls up in the top of the zone,” Loftin said. “But they are called strikes up in the big leagues. I think that was the biggest issue I had with ABS.”
No doubt there will be an adjustment period for players and fans alike when ABS is in use this spring.
“I’m curious to see how it is going to go for the guys that never got to experience it,” Loftin said. “But it will just be another day at the ballpark for me.”
