MLB Player Calls Out ABS Robot-Umpire amid Rule Changes: 'This Is Not Tennis'

While the use of the ABS challenge system during spring training seemed to go smoothly, it does not have a unanimously positive rating among MLB players.

One anonymous player told The Athletic's Jayson Stark they don't like the automated strike zone because it's moving the game closer to being tennis.

"This is not tennis," the player said. "Tennis doesn’t have a catcher, right? There’s a reason why."

Tennis uses hawk-eye technology that tracks the ball, so whenever a player wants to initiate a review, the response is instantaneous based on the trajectory of the ball.

The ABS system used by MLB in spring training isn't significantly different from what tennis uses. It utilizes a fixed strike zone that measures 17 inches wide (the width of home plate); and 8.5 inches in depth from the front and back of the plate.

Player height is also used to determine the top and bottom of the zone. The top of the zone is 57.5 percent of the player's height; the bottom comes in at 27 percent of the player's height.

There were 13 spring training parks set up with the ABS technology for MLB use. The system has been used in the minors since 2022 when it was adopted by the Florida State League (Single-A level). It was tested at the Triple-A level in 2023 and 2024, but the challenge system replaced it by the end of last season.

The challenge system allows for pitchers or hitters to challenge an umpire's call with a gesture, usually by touching their helmet or cap.

Since the system uses a fixed strike zone with technology set up in the stadiums, it takes almost no time to get the correct call. One of the primary criticisms of the ABS system is it would diminish the importance of catchers who are good at framing pitches to look like a strike.

While that is an extremely valuable skill to have since we are still entirely at the mercy of what the umpire judges a pitch to be, it can be argued that getting the call right should be the only thing that matters.

Given how quickly the ABS challenge system has been working its way through the minors, it seems like a matter of time before it gets put to use in real MLB games. The earliest it could be adopted for the regular season is 2026, but that's not guaranteed to happen at this point.