Automated strike zone (ABS) AKA robo-umps

seems like we should have a dedicated thread for this

something i learned from the middle of this long fangraphs article: https://blogs.fangraphs.com/q-are-we-not-men-a-we-are-robo/ is that while the traditional strike zone is three-dimensional, the ABS is two-dimensional. seems pretty rare that this could cause problems but i could see certain eephus pitches bypassing the ABS completely

https://blogs.fangraphs.com/wp-content/uploads/2025/02/MLB-Explainer.jpg

I'm all for it. Based on one minor-league game, not intrusive at all.

The funniest thing is that they need to measure hitters for their zone which apparently means a load of players listed heights will get exposed as fiction

I am kinda bummed out that the strike zone is no longer defined as a pentagonal prism

Although - now that I've read that fantastic article - I realise it still is! At least on non-challenge calls...

https://www.mlb.com/news/abs-challenge-system-mlb-2026

Salvador Perez is 4 for 4 on challenges. Anyone else doing as well so far?

Kirk has had two successful ones at critical moments in the game--I think he'll be among the best. (He did have an unsuccessful one early in yesterday's game.) Will this be a basic stat for catchers now, and where can you find info?

are catchers actually deciding when to challenge or are they getting a signal to challenge (or some combination of those two)?

so far i’ve mostly seen it displayed as a team stat, not a player stat

Just a guess: how much leeway catchers have will be similar to calling pitches. With Perez and Kirk, I have to believe the decision is theirs.

https://www.nytimes.com/athletic/7154534/2026/03/28/cb-bucknor-abs-challenges-eugenio-suarez-reds-red-sox/?unlocked_article_code=1.W1A.wlMm.HjEljswTod15&source=athletic_user_shared_gift_article_copylink&smid=url-share-ta

My understanding is that the challenge has to be made immediately, so the dugout has no say. Acuña had a funny one yesterday, pitch called a strike, he challenged and got it extremely wrong -- the entire ball was inside the zone, not even close.

Pretty clearly the catcher's call. 1) Yes, instantaneous. 2) Tyler Heineman, Jays' backup catcher, just won a big one against Nick Kurtz in the 8th, and he was greeted with much high-fiving back in the dugout--unlikely if the the decision was someone else's.

Baseball Savant has stats on all teams/players/individual info

overall succesful challenge rate with the bases loaded significantly higher than other situations.
will be interesting when there's some real data to go on

the bases loaded situation will surely end up below average because of desperation calls such as in late game/2 challenge remaining/high leverage/close game situations where you might as well throw a challenge out there on anything borderline, resulting in a much lower success rate

https://www.nytimes.com/athletic/7155626/2026/03/30/mlb-short-kings-height-measurements-changing-abs/?source=user_shared_article

Article of the year imo

”That’s a tough day for those guys,” said Padres outfielder Gavin Sheets. Sheets himself went from 6-foot-5 to 6-foot-3, but is still firmly a card-carrying member of the 6-footer club.

Haven't read it yet, but Posnanski's post today is on the ABS so far:

1) 165 total challenges

2) 78 by the batters — who were successful 42% of the time. They were able to flip 12 strikeouts and gain six walks.

3) 97 by the defense (all but five by catchers), and they overturned SIXTY-ONE calls (63% success rate), flipping 20 strikeouts and overturning six walks.

(Which adds up to 175, I see--Joe needs an AAS (automatic addition/subtraction system) installed.)

if i were a manager i would not want my batters challenging (except in do-or-die situations), they are just not physically in a position to see exactly where the ball crosses the plate. it's too bad there isn't a second-base coach or someone who could provide those immediate signals to a batter.

Acuña had a funny one yesterday, pitch called a strike, he challenged and got it extremely wrong -- the entire ball was inside the zone, not even close.

― I will edit thread titles like no one has ever seen before (WmC), Sunday, March 29, 2026 12:43 PM (yesterday) bookmarkflaglink

this happened with nasim nunez of the nats at the cubs game yesterday, the ball was fully in the strike zone

This was on MLB Now this morning and a picture to make is easier. Might have it in one of those links but I didn't click:

https://imgur.com/a/nzKGsDZ

https://imgur.com/a/nzKGsDZ.jpg

https://i.imgur.com/78Ky1qC.jpeg

if i were a manager i would not want my batters challenging (except in do-or-die situations), they are just not physically in a position to see exactly where the ball crosses the plate. it's too bad there isn't a second-base coach or someone who could provide those immediate signals to a batter.

I came to the opposite conclusion. When I see a batter complain about a strike call, he is nearly always right. The batters know their own strike zone extremely well. The umpire has a much tougher job, he has to learn 18 different strike zones, and adapt from batter to batter during the game.

IOW, I would expect the percentage of calls overturned by batters to be much higher.

CB Bucknor…an artist

https://www.youtube.com/watch?v=FJMX0xly5Zw

xp according to the mets booth catchers have had the highest success rate (60%-ish) vs hitters (40%-ish) vs pitchers (20%-ish) through opening weekend xp

...which clem already posted from posnanski

My understanding is that the challenge has to be made immediately, so the dugout has no say.

apparently the brewers dugout was flashing a green card for when it was OK to challenge (i'm guessing a high leverage situation as shown by analytics) but then MLB told them it wasn't OK to do so

https://i.imgur.com/8qGK8Ly.jpeg

Not going to do this everyday but do find it fascinating. I'm loving this, you need to get it right and it's not taking a lot of time. this is thru last nights games.

I’d love to have an opinion on that but

Request: Please stop using imgur

The image:

Batters: 52/103 = 50.5%
Catchers: 70/118 = 59.3%
Pitchers: 2/6 = this one's basic!

Agustin Ramirez seems good at this

https://www.youtube.com/watch?v=4gkkB8tuCCQ