Since the invention of the virtual strike zone in 2002, baseball fans have wondered how long human umpires would last. The debate of authenticity versus accuracy began and seemed to intensify by the year. While the MLB’s longevity of tradition and culture is highly regarded, missed call after missed call just seemed to raise too many questions. In 2024, MLB umpires called 27,336 pitches incorrectly, and 1,637 of these missed calls resulted in strikeouts.

In 2019, the MLB began experimenting with a middle ground between human umpiring and technology, as they created the Automated Ball Strike (ABS) Challenge System. The rules on the new system are as follows, per the MLB: Teams will have two challenges per game, and only the batter, pitcher, or catcher can challenge the call. Challenges must be made immediately after the pitch, which will not allow for the revision of film prior to the challenge. If the team wins the challenge, they will retain the challenge, but if the challenge is unsuccessful, the team will lose that challenge. The system was implemented into the Independent Atlantic League in 2019 and was implemented into the Triple-A level in 2023, for a more serious test with a much larger sample size. 

At the conclusion of the 2024 MiLB season, player feedback was positive, and it was announced that the system would be used in stadiums with Hawkeye Tracking installed. The goals of the implementation were to both determine whether the system was ready for real-deal MLB games and to give players an opportunity to get used to the system if it is to be officially added. As of early on, players seem to have caught on quickly and have offered a majority of positive feedback. The emerging trend seems to be that younger players, especially those who had experienced the system at the AAA level, seem to prefer it, while some older veteran players claim that it takes away aspects of the mental game, and the art of pitching to the umpire’s zone, rather than just the zone that they are instructed to call.

The pros can be summed up as a step in the direction of integrity. The frequency with which the rulebook strike zone is called incorrectly is exclusive to baseball. No other major sport features a number of confirmed wrong calls even close to the tens of thousands that MLB umpires miss every season. There’s obviously an argument based around the minimal severity of missed pitch calls, but if you’ve watched baseball enough, you know that ball strike calls shape how at-bats transpire.

 According to MLB’s Statcast, hitters in 2021 batted .159 with two strikes, almost 100 points lower than the overall league average of .244. Missing a call on a ball in a 1-1 count reduces the probability of the batter recording a hit severely. When you apply the fact that 30 teams play 162 games a year, you can do the imaginary math equation. The lack of perfect accuracy ends up taking away hundreds of could’ve-been hits, and should’ve-been walks and strikeouts, as well as adding false walks and strikeouts, and vice versa with adding to the probability of hits. 

While these factors would probably be offset for the most part with perfectly accurate umpiring, the results would be more legitimate. Every strikeout would be a legitimate strikeout, every walk would be a legitimate walk, and so on. As noted beforehand, this is only a step in the direction of integrity. Complete accuracy is likely a decade or more down the road. The other positive aspect of the challenge system is the entertainment of it. Similar to the path that the Associated Tennis Professionals (ATP) took, a challenge system with a similar entertainment feature was put into place in 2006, and is currently being replaced in many tournaments with perfect accuracy line calling. The MLB seems to be on a very similar trajectory, as the ABS Challenge system is a fun twist to the broadcast as well as the live game, and will add a sense of confidence into the umpiring of games.

From a more modern, statistical standpoint, there seems to be no downside to improving the integrity of the game. However, there are two primary refutations to the progression towards automated umpiring. The most defensible point being that the value of a catcher’s ability to frame pitches would be lost. Framing, the skill of deceiving an umpire with how the ball is caught, would matter less with the ABS Challenge System, and ultimately wouldn’t matter at all with a fully automated system. This would have ripple effects on stolen base efficiency and prioritizing different skills among catchers, as a player with better hitting ability would be prioritized over a player with better framing ability. 

While the loss of the value of framing is more concrete, concerns among the players about the “feel” of baseball changing, are having a stronger effect on negating the process of integrating the challenge system. These comments are coming primarily from pitchers, who have a variety of reasons why they prefer the umpire’s decision to be the only form of decision. The most commonly expressed concerns are regarding the Hawkeye Tracking system not being calibrated the same in every stadium, causing problems with consistency from place to place. The other argument, common from older pitchers, is that working with the umpire’s established zone is an important part of the game. 

After his Spring Training debut, 42-year-old Justin Verlander of the San Francisco Giants was asked about his thoughts on the new system. Verlander stated it would be good for the future of the game, but also admitted frustrations, stating that  “[The umpire] likes to call the high one, but doesn’t like to call the low one. That’s the game of baseball. I don’t want to take that away.” Verlander, a 3-time Cy Young award winner and 2011 MVP, is the type of respected player whose voice is heard loudly. This opinion is shared among several throughout the league, although most agree with his view that the change will be good for the future of baseball.

To conclude, the MLB’s ABS Challenge system has a plethora of implications and ripple effects, some of which we cannot identify at this time. What we know is that the new rules will make a divot in the issue of umpire accuracy. However, we also know that baseball will certainly have a different feel for both players and viewers. While there are some concerns, I strongly believe the system will be voted in, and we’ll be seeing challenges in real games come 2026. Once finalized, the next looming question will be whether or not to go to full-scale automation with the ABS system. However, that debate is a whole different story.