For over 150 years, baseball has relied on the human eye to call balls and strikes. Until now, umpires had been entrusted — across all levels of the game — to call games to the best of their abilities, with no technological help. An umpire’s strike zone judgment is famously known to cause both verbal, and in extreme cases, physical, altercations with players and managers. 

However this banter between teams and umpires has become a staple of the game. Fans have grown accustomed to seeing players throw their helmets in disgust over a call and managers getting within inches of an umpire’s face, close enough that you couldn’t even slide a notecard in between them. 

In recent years, there has been a push for an automated strike zone. People began to criticize Major League Baseball for continuing to deal with human error when, theoretically, a robot could be correct every time. Almost every televised MLB game has a strike zone green-screened above home plate; people can tell in real time if umpires made a correct call.  

In response to these pleas, MLB commissioner Rob Manfred implemented the full Automatic Ball-Strike system in the independent Atlantic League in 2019. 

In its first implementation, the ABS system called every ball and strike for the entire game. Umpires were there only to make calls on the basepaths and ensure the system was running smoothly. 

In 2022, the ABS challenge system was introduced in the Florida State League. In this version of ABS, home-plate umpires still call balls and strikes, but Hawk-Eye Technology — a high-speed video system used by the MLB — runs behind the scenes to monitor the exact location of a pitch relative to the hitter’s strike zone. This meant players could challenge a call by tapping their helmets if they thought the umpire made an incorrect call. 

Minor League Baseball tested the challenge system and the full ABS system in the 2023 and 2024 Triple-A seasons. After testing fans, players and managers in the 2024 season, the league came to the consensus that the challenge system would be more beneficial.

The results revealed that fans and players still wanted to have a physical umpire. The MLB implemented umpires full-time in 1901, and they have been present ever since. The game would not be the same without a textbook strike-three call or a classic umpire and manager dustup. 

This year, MLB is implementing the challenge system in spring training. The system will be in place for nearly 60 percent of spring training Games as a trial run for the MLB to determine if the system is feasible at the major league level. 

“Do [players and fans] feel like baseball is a better game? Is it more fair?” MLB Executive Vice President for Baseball Operations Morgan Sword said. “This is a pretty big decision for the game of baseball that we want to make sure to get everybody to weigh in on.”

The MLB dealt with a similar situation 17 years ago. 

In 2008, the MLB was the only major North American professional sports league to not have any form of instant replay. In response, the MLB implemented a very elementary instant replay review system. In this format, only the umpire crew chief could initiate a review, and it could only regard boundary home run calls — whether or not a home run went over the wall or was fair or foul. 

In 2014, the MLB implemented the current system we see today. Each team’s manager is granted one challenge per game and is allowed more challenges if the previous one was correct. Late in the game, from the eighth inning on, the umpire crew chief is allowed to initiate his own review. 

The current system is also much more expensive than the 2008 version. Teams are now allowed to challenge fair/foul balls in the outfield, force outs and tag plays, and whether a batter was hit by a pitch. Nearly every aspect of the game can be challenged and checked by digital review … except for balls and strikes.

The trial run of the ABS system in spring training grants each team two challenges apiece at the start of the game. Successful challenges are retained. Hitters, pitchers, and catchers can initiate a review by tapping their head immediately after the umpire’s call, and the dugout cannot intervene. 

Early reactions to the ABS system have, expectedly, shown mixed reviews, albeit in a positive tone.

“I thought today [the system] was great,” Diamondbacks starting pitcher and 2021 National League Cy Young winner Corbin Burnes said. 

After retiring the first batter he faced in the top of the first, Burnes threw a 1–2 pitch down and away for a ball, according to the umpire. His catcher, Gabriel Moreno disagreed and tapped his helmet in succession. The strike zone was shown on the scoreboard, and it revealed Moreno was correct. The pitch nicked the lower left-hand corner. Strike three. Burnes retired the next batter and his outing was over. 

“As of today, I liked the ABS,” Burnes continued after his outing. “Ask me the next time I go out.” 

Burnes’ remarks encapsulate why the MLB is hesitant to implement the system full-time. Players and fans are still likely to be unsatisfied with the results. When calls go their way, they will be in favor. When calls go against them, they will wish they were still in the days when an umpire’s call was final. 

But for now, an umpire’s call is still final. Any implementation of the ABS system will drastically change the game which has been relying on umpires for over a decade.

“I don’t think [the ABS challenge system] is bad,” five-time American League Cy Young winner Justin Verlander said when asked about the system. “I definitely think it’s going to take some time to get it right, just like everything that’s been implemented in the game. We don’t know the ripple effects of it. But in the end, in big spots everyone wants the call to be right.”

Verlander is right. Most of the push for an automated system stems from people wanting the game to be called correctly in big moments. But for so long, the game of baseball has been intertwined with umpires. And to a certain extent, bad calls are a part of the game.

The ABS system cannot be implemented into the MLB regular season until 2026, at the earliest. 

In the coming years, MLB will need to discover what it values more: the history or the future of the game.