Beginning with this afternoon’s Dodgers-Cubs game, MLB has announced that they’ll be testing their rob-ump technology, which is officially the Automated Ball-Strike System Presented by T-Mobile (a hideous phrase I promise you I will never type out again) through spring training. It is not in consideration for use in the majors this year, but this test opens the door for its use as early as the 2026 season.
The trial will run in 13 Grapefruit and Cactus League parks with the Hawk-Eye system installed (representing 19 teams, as many Cactus League parks are shared), so it will cover about 60% of spring training games. TD Ballpark has Hawk-Eye because of StatCast’s coverage of the Level A Florida State League, so the Jays will be one of the teams involved.
It will be a challenge-based system, in which each team begins the game with the ability to challenge two ball/strike calls. Challenges can be made by the pitcher, the catcher, or the batter, but not by the manager or anyone else in the park. Successful challenges are retained. The challenge has to be immediate, unlike challenges of plays in the field, so the players aren’t allowed to wait for someone in the dugout or booth to watch a replay and recommend what to do. An animation of the Hawk-Eye ball tracking will be shown on the video board, similar to how challenges look in tennis (which uses the same system), so fans will get to see how the review goes. In minor league testing, challenges have taken an average of 17 seconds, so this shouldn’t slow games down noticeably.
The ABS system was first tried in the independent Atlantic League in 2019, and has been used in all AAA parks since 2023. When implemented with full robot umpires, it hugely increased walk rates, because the strike zone as called by humans is significantly bitter than the strict rules-based one used by the robots. Humans squeeze pitchers a little on the corners, especially up, but their zone is pretty round and so balloons outside the strict zone at the top and bottom and on the sides, increasing the total area. The automatic zone also doesn’t change size and shape with the situation, while human umpires will tend to give the pitcher a little grace on 3-0 pitches and maybe give the batter the benefit of the doubt on 0-2 counts. The challenge system has a much smaller impact than the fully automated version, because players see the zone about the same way umpires do most of the time, but the general direction of change remains the same.
The effect on the Blue Jays of bringing in automated balls and strikes isn’t clear. Last year, their hitters had the 8th lowest chase rate by StatCast’s tracking (which should accord with the challenge system), so it should help their offense a little. On the other hand, their pitchers had a slightly below average rate of pitches in the zone, and Alejandro Kirk grades as an elite framer, so they might lose some extra strikes that were benefiting them on that side of the ball.
Over at The Athletic, Jayson Stark has a piece with some good notes on strategy for dealing with the system. The big takeaways are not to emotionally challenge calls, which will be more of a challenge for some hitters than others. Teams might also want to decide who has a green light and who doesn’t, or in what situations to gamble, because the whole team shares the two challenges and throwing one away early on a bad decision or an unimportant moment could hurt later. On defence, it seems that teams should rely much more on their catchers, who have a better view of the zone than even the ump, and keep the choice out of the pitcher’s hands. It’ll be interesting to see the strategy evolve over the course of the month as teams get used to the rules.
Personally, I don’t really object to the system, although I also doubt it’ll make all that much difference. I like keeping framing as an aspect of the game, partly because Kirk adds so much value that way and partly because I just like the game to be handled by humans where possible, even if that sometimes cuts against my team. So I’d oppose robot umps. But the challenges strike me as fine. They can prevent some of the egregious errors umpires make, and I bet will have some effect on shrinking the called zone towards the actual zone as umpires get used to seeing which of their calls are overturned, but hopefully without being too intrusive overall. From watching some Bisons games with the challenge system in place, it’s been pretty tolerable as applied in AAA. What do you think? Should MLB consider implementing this in real games next year?