SAN FRANCISCO – For more than a century, each pitch thrown in a Major League game has been judged by one set of eyes: those belonging to the home plate umpire.
That officially changed on Opening Night. Yankees shortstop José Caballero triggered the first Automated Ball-Strike (ABS) challenge powered by T-Mobile in a big league game, tapping his helmet in the fourth inning Wednesday in New York's 7-0 win over San Francisco at Oracle Park.
ABS Challenge System, powered by T-Mobile
• See what happened on the first-ever ABS challenge
• Everything you need to know
• A visual guide to how ABS works
• Here are Major League Baseball's ABS firsts
• What does all the data mean
• Players get strike zones measured
• Player poll: Who'll be best at ABS challenges?
• ABS Challenge Dashboard
• ABS Challenge Leaderboard
Caballero challenged home-plate umpire Bill Miller’s strike call on Giants starter Logan Webb's sinker on the high-and-inside part of the plate, and the call was upheld.
While ABS is new to MLB, it’s already familiar to many fans and players. The system has been tested in the Minor Leagues since 2022 and was used in Major League Spring Training in 2025 and ‘26 before gaining approval from the Joint Competition Committee last September.
The ABS Challenge System tracks the precise location of each pitch, relative to the specific batter’s zone, which is calibrated to his height and measured to the fraction of an inch.
It represents a hybrid model, preserving human umpires for the vast majority of pitches while offering a mechanism to correct the most obvious misses.
A pitcher, catcher or batter can challenge a ball or strike call by tapping their hat or helmet immediately after the pitch. There is no input from the dugout. Within seconds, the result is displayed on the stadium video board and broadcast to viewers.
Each team is allotted two challenges per game and retains them if successful, introducing a new layer of in-game strategy.