ABS system update: The MLB umpires getting exposed the most as we enter May

As the 2026 MLB season races into May, the ever-shifting standings aren't the only thing we're paying attention to. There's also the game within the game — no, not Framber Valdez vs. everyone else on the field, but umpires against the new ABS challenge system.

The advent of the strike zone overlay on most television broadcasts — plus sites dedicated to tracking their performance — has brought home-plate umps under increased scrutiny in recent years. But 2026 marked the first time they'd be faced with actual accountability, in the form of pitchers and catchers being able to challenge calls they thought were incorrect.

Which umpires were ready for their close-up, and which might wish they were getting a little less attention? At this point, with nearly a month and a half of data, under our belt, we're beginning to find out the answer.

Which umpires have the worst track record with ABS challenges?

Below are the 10 home-plate umpires with the highest rate of challenges overturned. (In order to separate the signal from the noise a bit, we set a minimum of nine pitches challenged.) Before you ask: Yes, CB Bucknor is featured. But maybe not as early as you think!

First, in the interest of fairness, we'll provide some context. Most of the umpires on the list above have seen anywhere from 1,100 to 2,000 total pitches, of which the total that have been challenged is but a very small fraction. Of course, those numbers might look different if pitchers and catchers were given an unlimited number of challenges, rather than two that they have to use judiciously, but still: It bears repeating that, for the most part, umpiring is in a pretty good place, and is certainly lightyears better than it was even 10 or 15 years ago.

All of that said, an overturn rate of two-thirds or higher is less than ideal, to say the least. Especially because a lot of these names aren't a surprise: Buckner was a mortal lock, despite not having nearly as much volume behind the plate as a lot of his peers. And there are plenty of other veterans, guys like Kulpa and Fletcher, who have been at this for decades now.

Again, this is an incomplete evaluation of an umpire's work. But it goes to show just how many pitches are called incorrectly during the average big-league game, even now, after plenty of fresh blood has worked its way through the ranks and training is better than it's ever been. As the future of automated umpiring is debated moving forward, that fact should loom large.

ABS is making all too clear which MLB umpires are getting left behind

I really am empathetic to the plight of a lot of umpires. Sure, there are egregioue cases like Bucknor, guys who leave such a significant imprint on the game that it can't be ignored. But for the most part, the dirty truth is that umpires do a pretty good job, despite that job being hard — pitching is better than ever before, which means it's more difficult to track than ever before.

Still, these numbers sure make it feel like a full roboump system is inevitable. We have so much technology accessible to us from the comfort of our home now that fans will not rest until we know that human error has been removed from the process as much as possible. I have some misgivings about that mindset — for one, there's something to be said for leaving sports as human as possible, and for another, part of the whole point of this exercise is to embrace the uncertainty inherent in life — but I'm clearly in the minority.

Even at the high end of the profession, plenty of misses are going to happen, and those misses will inevitably affect the outcomes of games. And the more we're aware of those misses, the larger they loom, and the more outraged we'll get by even the more minor infractions. I don't really have patience for umpires who feel embarrassed by the ABS system, but I do understand the impulse, because it feels like they're watching their profession dissolve in real time.

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