Major League Baseball’s move toward “robot umpires” is no longer theoretical. It’s happening now — and already influencing games in measurable ways.
The league’s Automated Ball-Strike system, known as ABS, is being used this season in a challenge format that allows players to question ball and strike calls using computer tracking. Early results suggest the system is accurate and impactful, though not without questions about how it fits into the sport long term.
Through the first 12 games of the regular season, teams have won 61.3% of their challenges, going 19-for-31 — a higher success rate than what was seen during testing in the minor leagues and spring training.
The system relies on Hawk-Eye technology, using 12 cameras installed around each stadium to track pitches and determine whether they pass through the strike zone. MLB says the system can measure pitch location to within about one-sixth of an inch.
Unlike a fully automated system, human umpires still make every call. Each team is given two challenges per game, and only the pitcher, catcher or batter can initiate one. A challenge must be made almost immediately — within about two seconds of the call — typically by tapping a helmet or cap.
If the team that challenges the call is correct — meaning the original call was wrong — the call is overturned and the team keeps its challenge. If the challenge is unsuccessful, the team loses it.
Once a challenge is made, a visual of the pitch and its location within the strike zone is shown on the stadium scoreboard and on broadcasts. The review is quick, with calls confirmed or overturned in roughly 13 seconds.
The system is already affecting outcomes.
In a game between Pittsburgh and the New York Mets, Pirates slugger Oneil Cruz appeared to draw a walk on ball four. But Mets catcher Francisco Alvarez challenged the call. The system showed the pitch clipped the inside corner, overturning the call to strike three and ending the at-bat.
In another case, Phillies reliever Zach Pop challenged a late-game walk call against Brandon Nimmo. The system confirmed the umpire’s original call, allowing the walk to stand.
Phillies manager Rob Thomson said he supported the decision to challenge, even though it didn’t go his team’s way.
“I was good with it. It was a 10th of an inch off,” Thomson said. “That pitch decided an at-bat late in the game, we’ve got the lead. On the defensive side, you want to use that challenge.”
The technology itself has been years in development. MLB has tested versions of ABS in the minor leagues since 2019, including extended use at the Triple-A level beginning in 2022. The current challenge system represents a compromise — keeping the human element while adding a layer of precision.
Still, the strike zone being enforced by ABS is not exactly the same as the one fans are used to seeing.
The system uses a rectangular strike zone based strictly on a batter’s measured height, taken without shoes. It evaluates the pitch at the midpoint of the plate, rather than across its full depth. By contrast, the rulebook defines the strike zone as a three-dimensional space, and in practice, umpires have historically called a zone that can vary slightly in shape.
Major league umpires already call roughly 94% of pitches correctly. But the remaining margin for error can have major implications — especially in close games or late innings.
So far, players appear to be using challenges strategically, often in high-pressure situations like full counts or two-strike pitches.
For MLB, the early results suggest the system is doing what it was designed to do: improve accuracy without significantly slowing the game.
Other sports offer a glimpse of where this could lead.
Professional tennis has fully adopted Hawk-Eye technology for line calls, eliminating human line judges entirely after years of using a challenge system. Players were initially given a limited number of challenges per set before the sport transitioned fully to automation.
Baseball may or may not follow that path.
For now, the familiar rhythm remains — the umpire’s call, the catcher’s reaction, the crowd’s response.
But as technology becomes more embedded in the game, one question lingers:
Will baseball eventually move beyond the human call of “ball” or “strike” — or are those moments as much a part of the game as hot dogs, popcorn and the singing of “Take Me Out to the Ball Game”?
