A called strike, a safe runner, an out at first base, or other judgment calls— every decision in MLB was for the umpires to make until now. For a century, players and managers could only appeal and argue game-changing calls, including getting tossed from games in specific cases, but the umpires had the last word. The human element of the game added more character to the high-intensity sport.

Now, with the rapid evolution of sports technology, baseball is also changing. MLB used technology to add another layer of authority to decision-making in baseball. The Automated Ball Strike Challenge system, or robot umpire, is the latest technological addition to shake up the big leagues. 2026 marked the beginning of a new era in baseball under the surveillance of robot umpires.

“I commend the Joint Competition Committee for striking the right balance of preserving the integral role of the umpire in the game with the ability to correct a missed call in a high-leverage situation, all while preserving the pace and rhythm of the game,” Commissioner Rob Manfred said in a statement, per MLB.com.

Introduction of the Automated Ball-Strike System

In an effort to end arguments between umpires and managers over ball-strike calls, MLB introduced the ABS challenge system in 2026. A huge success in its first season, the ABS overturned 5,686 calls out of 10, 557 challenges. An ESPN report provided the numbers in detail.

“Robot umpires overturned 54% of challenged calls in the first season of the automated ball-strike system as catchers were far more successful than batters,” wrote the media outlet on X.

According to ESPN, William Contreras stopped 5.2 projected runs, leading catchers in the big leagues. Cleveland’s Patrick Bailey ranks second with 5.1 projected runs prevented, followed by Francisco Alvarez (4.5), Freddy Fermin (4.3), Carter Jensen (4.3), and Drew Romo (4.3).

Among the batters, Jose Altuve topped the charts with 5.6 projected runs gained from ABS challenges. Moreover, each game recorded an average of 4.35 challenges in the regular season. The postseason is also not an exception to the ABS.

During the Philadelphia Phillies’ 4-3 win over the Atlanta Braves in Game 2 of the NL Wild Card Series, JT Realmuto scripted history with the first game-ending ABS challenge in the postseason. At the bottom of the tenth, after the umpires ruled Andrew Painter’s 0-2 pitch a ball, Realmuto used the Phillies’ last ABS challenge to overturn the call and end the game.

According to the rules, each team gets two challenges per game. Each wrong appeal docks one challenge. With ABS, teams need to be selective about when and how to use them.

“It’s like a new muscle for players to learn,” said the Yankees manager Aaron Boone. “You have instincts about what to do in certain situations. This is a new instinct of knowing when to challenge and, instinctively, within a second, Oh, that’s a ball. What’s the situation?”

Twelve Hawkeye Cameras are used to track the game. Seven cameras track player movement, base-running, positioning, and umpire paths. Five cameras are dedicated to tracking baseball trajectories, spin rates, velocity, and exact coordinates in three-dimensional space. The umpires no longer determine the strike zone for each player.

However, it does not undo the umpires’ role. Despite the introduction of the ABS, the first level of authority rests with the umpires. With MLB keeping the system appeal-based, technology enters the picture only when a team challenges. MLB is currently operating under a hybrid model rather than letting technology dictate the game entirely. Yet it has not been easy for the veteran umpires to cope. Seven veteran umpires, including Brian O’Nora, CB Bucknor, Marvin Hudson, Laz Diaz, Andy Fletcher, Tony Randazzo, and Lance Barksdale, retired at the end of this season.

But technology had infiltrated the traditional game long before ABS arrived. Instant replay is one of them.

Technology in MLB before ABS

In 2008, MLB officially introduced instant replay to review disputed home run calls. The first MLB instant replay was used to check a twelfth-inning home run by the Yankees legend Alex Rodriguez against the Tampa Bay Rays at Tropicana Field. Six years later, in 2014, the league expanded the scope of replay, letting managers challenge most of the calls on-field. The league allows each club one manager challenge in the regular season and two manager challenges in the postseason and the All-Star Games.

Replay officials at MLB’s Replay Command Center use multiple video feeds to verify and decide whether the on-field call requires an overturn.

The introduction of instant replay was a major development but not unique to baseball. Sports like tennis have been using Hawk-Eye technology for a long time to determine whether a ball was in or out. Soccer has also introduced VAR to help officials review goals, penalties, offsides, and red-card incidents.

Coming back to baseball, the introduction of instant review did not make the umpires redundant. They still made the original call, but it was no longer final.

According to ESPN, “There were 1,294 team challenges, an increase from 1,197 in 2025. Among the challenges this year, 243 calls were confirmed (18.8%), and 367 were allowed to stand (28.4%) when there was not clear and convincing evidence to overturn them. The average time of a review was 1 minute, 25 seconds.”

Technology can only help the sport to function smoothly, but humans must operate it.