Key Points
Bullet point summary by AI
- As the Automated Ball-Strike Challenge System completes its inaugural month in the 2026 MLB season, home-plate umpires face unprecedented scrutiny over their challenge overturn rates.
- Early data reveals several veteran umpires with decades of experience are seeing over 75% of their calls overturned after team challenges, highlighting systemic inconsistencies in pitch judgment.
- The growing transparency of ABS challenges is intensifying debates about the future of human umpiring, with fans and teams demanding near-perfect accuracy in pitch calls.
We're now nearly one full month into the 2026 MLB season, which means we're nearly one month into life with the Automated Ball-Strike Challenge System. That feels like enough time for everyone to have gotten a sense of how the system actually works — what the new, tailored strike zones look like and how best to deploy challenges over the course of a game — and to have adjusted their behavior accordingly.
It's also enough time to start rendering judgment. Umpires have done more than a little belly-aching over the last few weeks about how ABS is putting them unfairly under the microscope, about how they're being embarrassed in front of thousands of fans. To which we say: OK? The entire point of this exercise is supposed to be getting each call as right as possible, and if you're complaining about doing just that, well, maybe your heart isn't really in the right place.
Then again, if we were some of the umpires on the list below, we probably wouldn't be too happy either. Because the early results reveal some pretty awful performances.
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!
Umpire | Pitches challenged | Overturn rate |
|---|---|---|
Andy Fletcher | 21 | 85.7% |
Paul Clemons | 11 | 81.8% |
Ron Kulpa | 14 | 78.6% |
Junior Valentine | 9 | 77.8% |
CB Bucknor | 9 | 77.8% |
Chris Segal | 22 | 77.3% |
Mike Estabrook | 21 | 76.2% |
Cory Blaser | 11 | 72.7% |
Charlie Ramos | 25 | 68% |
Brian Walsh | 15 | 66.7% |
Some context is needed here. Even the highest number of pitches challenged is a small fraction of the 1,100-1,600 pitches that most home-plate umpires have seen so far this season; 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.
That said ... well, suffice to say that an overturn rate of north of 75% isn't great, and who knows what the results would look like if teams weren't limited to two challenges a game. It should be no surprise that Bucknor is one of the names on this list, 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 Estabrook, 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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