MLB robot umpires, explained: What to know about ABS challenge system and how it works for 2025 All-Star Game

The MLB is continually seeking ways to enhance its on-field product. Teams play 162 games a year, and it's hard to retain fans' attention for that long. 

In recent years, the league has increased the size of bases to try to entice more steal attempts. It has also introduced a pitch clock to speed up games significantly. One of the most controversial topics has been the implementation of "robot umps" around the MLB. Some fans want them, saying that if we have the technology to get all of the calls correct, we should. Other, more traditional, fans think that one of the best aspects of baseball is that it's a game that has human error. 

As with most rules with a serious chance of being implemented, robot umpires — also called "automated balls and strikes" (ABS) — have been used in the minor leagues. It sounds more intense than it is. The ABS name suggests that every pitch will be ruled a ball or a strike by a computer, but we aren't there yet. 

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Here's more on the MLB's ABS challenge system and how it will be incorporated into the 2025 MLB All-Star Game. 

MLB robot umpires, explained

ABS was tested in the minor leagues in 2021 and was implemented in 2022. It didn't make its way to the majors until spring training in 2025. Again, the system is not an automatic review of every pitch that is thrown, like the name suggests. Instead, it is a challenge system.

The MLB will implement the same rules it used for ABS in spring training for the 2025 All-Star Game. Each team will start the game with two challenges each. After a pitch and the subsequent call from the umpire, only the pitcher, catcher, or batter who is in the box may challenge the call. To do this, they will signal by tapping the top of their cap or helmet. The challenge signal must also be given immediately, not after receiving intel from coaches or teammates in the dugout.

The umpire will call time, and the pitch will be reviewed on the video board with the correct call. If the challenge is successful, it will be retained. If the challenge is not successful, it will be lost and deducted from the two challenges that the team began the game with. 

What is ABS?

The term is a little misleading. It stands for "Automated Balls and Strikes." This makes it sound like there won't be an umpire behind home plate, instead giving way to an automatic call made after every pitch. While we may get there one day, that isn't the case.

As it currently stands — and as it will be in the 2025 MLB All-Star Game — ABS is just a challenge system where the pitcher, catcher, or batter will be able to challenge two pitches during the course of the game. If they win the challenge, their team keeps the challenge. If not, they lose it. 

When did ABS begin?

The MLB has been testing ABS in the minor leagues since 2021. It has been implemented in some fashion in the lower levels since 2022. After repeated success, ABS made its way to the major leagues for the first time during the 2025 spring training. For the first time during the regular season, ABS will be used at the 2025 MLB All-Star Game. 

How many challenges do teams get?

Each team will begin the game with two challenges apiece. When a pitcher, catcher, or batter challenges a pitch call, one of the team's challenges will be used. If they are successful in their challenge, it will be retained. If they aren't and the umpire's call was correct, the team will lose that challenge. 

Will umpires be at the 2025 MLB All-Star Game?

When you hear the phrase "automated balls and strikes," it makes you think that umpires won't be needed anymore. Currently, the way the ABS is used does not support this. An umpire will be behind home plate of the 2025 MLB All-Star Game and will make a call on every pitch in the game.

The only thing that changes is that some of the umpire's calls can be challenged. They will still be behind home plate, will rule on pitches, and will also be on hand for any plays at the plate.