MLB Automated Ball-Strike System Explained

Baseball’s getting a high-tech makeover this spring, with “robo umps” making their debut in major league games starting Thursday when the Cubs face the Dodgers in Arizona.

It’s not quite the full robot takeover some fans might imagine. Instead, MLB is testing out a challenge system that lets teams question close ball and strike calls – kind of like instant replay for the strike zone.

Here’s how it works: Teams get two challenges per game. If they’re right about a questionable call, they keep the challenge. If they’re wrong, they lose it.

The system, officially called ABS (Automated Ball-Strike), uses special cameras to track every pitch and figure out if it’s really a ball or strike. What’s pretty cool is that it creates a custom strike zone for each batter based on their height and stance – so Aaron Judge doesn’t get the same strike zone as Jose Altuve.

“I would be interested in having it in ’26,” MLB Commissioner Rob Manfred told reporters last fall, hinting at when we might see this in regular season games.

The tech’s already been tested extensively in the minor leagues since 2019. Triple-A teams used it last season, trying out two different approaches – some games were fully automated, while others used this challenge system MLB’s now testing.

When a team challenges a call, it’s surprisingly quick. No dramatic flag-throwing like in football – just a quick check that takes about 15 seconds.

Not every spring training game will have this system though. Only ballparks with the right technology can use it. The Arizona Diamondbacks will get the most practice with it (29 games), while the Cubs will only see it seven times.

The umpires’ union has already given MLB the green light to use this system in regular games. Since MLB controls most votes on the committee that makes rule changes, it’s really just up to them to decide when to roll it out full-time.

“There’s two sides to that test,” Manfred says. “What the clubs think about it and what the players think about it. We’re going to have to sort through both of those.”