There's loads of ABS data from last season. What does it all mean?

Welcome to the future. No robots required.

For the first time, ABS (the Automated Ball-Strike Challenge System, powered by T-Mobile) has come to regular-season and postseason Major League play, after several years of testing in Spring Training, the All-Star Game, and the Minor Leagues. While you’ll see it for the first time for real on Opening Night, it’s already been going on in every Spring Training game – 291 times, to be exact, through Tuesday's games.

If you want to learn more about the rules and the hows and whys, look no further than Anthony Castrovince’s excellent rundown or Adam McCalvy’s look at how players actually get measured for their individual zones.

But what you’re also going to want to know will be about the trends and strategies behind all of this. Who’s going to be good -- or not so good -- at challenges? What effect will this have on catchers? Do challenges get saved for more impactful times?

Until the regular season starts, we can’t know those answers for sure; Spring Training, after all, is a time for experimentation more than winning, and a team’s lineup in the first inning looks very different from who’s still out there in the ninth. But we have more than just a few days' worth of spring data at hand, too, because all of this was in effect at Triple-A in 2025. Now available on Baseball Savant’s ABS dashboard, we can get a pretty good idea of how real pro ballplayers handled the sport’s newest wrinkle.

So: What did we learn from the Triple-A season? It’s absolutely crucial to note that Minor League players are (mostly) not Major League players, and Minor League umpires are (mostly) not Major League umpires, so we shouldn’t expect a 1:1 repeat of all this in the big leagues in 2026. But it’s a good place to start.

Here are 10 things we’ve learned so far …

1. It’s 50/50 overall, but fielders are better at this than batters.

In Triple-A in 2025, the overturn rate was almost exactly 50%. Batters weren’t as good (45% success rate) as fielders (nearly 55%). (As for what specifically we mean by "fielders," more on that below.)

Those numbers correlate reasonably well with what we’ve seen in the first few days of 2026 Spring Training – the overturn rate is 52%, and batters aren’t as good (48% success rate) as fielders (55%).

That’s intuitively expected. Catchers can take the long view of the game more than hitters, who have only brief times at the plate to challenge, and catchers are crouching with a similar view of the zone as the umpire.

Don’t gloss over the importance of the 50/50 success rate, though: If these challenges are going to come only on pitches close enough that you think the umpire was wrong, and it’s still only a 50/50 shot that the player is correct, well, that has to say something really good about how well umpires do their job – which is far, far better than the credit they’re given. Remember that unlike umpires, who must call everything, challenging players can cherry-pick good opportunities – and they’re still only right half the time.

Fielders, for now, includes both the catcher and pitcher, either of whom is allowed to challenge, simply because the way the Minor League data was collected didn’t specify who initiated it. At the Major League level, at least, expect that to be overwhelmingly backstops, at least the way managers are talking.

Chris Sale, notably, has already said that he’ll never take advantage of initiating a challenge. “I fully agree with him,” said San Diego starter Michael King.

“My early thought … I don't think the pitchers should ever challenge,” Twins skipper Derek Shelton said to ESPN, and Astros manager Joe Espada said, “I highly encourage [pitchers] not to do it.” On the other hand, Yankee manager Aaron Boone seemed open to letting his hurlers try.

We’re guessing there will be a few – but not many.

2. Relatively few pitches get challenged.

If you’re worried this is going to take over the game, don’t be.

Last year in Triple-A, there were just over 861,000 pitches. On them, there were 9,432 challenges, which means that slightly more than 1 percent of all pitches resulted in a challenge. Since the overturn rate is roughly 50/50, well, 0.5% of all pitches ended up being overturned. That’s really not very much.

Of course, not every pitch is a challengeable one. You can’t challenge a swing, for example. You can’t challenge if you’ve already used up your challenges and have no more available. You’d never want to challenge if the call went your way, obviously. You’d never bother if it went against you and was clearly correct.

Among challengeable pitches – non-swings that went against you, with challenges remaining – it was still only 3% of the time that the hands would tap the helmet. If you’re just looking at takes on the edges of the zone, it was under 7% of pitches that got challenged. The reason why is clear: because so many borderline pitches are borderline enough that it’s not obvious to risk the challenge.

That’s not to say you won’t see challenges, because you will. Almost every Triple-A game last year, 98.5% of them to be exact, saw at least one challenge. But only one in six games had four or more overturned calls – and 61% of games had two or fewer overturns. Umpires, again, are excellent, despite the myth that says otherwise. (“Maybe we’ll find out it’s pretty hard to be an umpire – I think that’s probably what we’ll find out,” noted Cubs manager Craig Counsell.)

Not a single game ended with a challenge, for what it’s worth. (Though it did happen in prior years.)

3. Challenges really do get saved for the end – but there are more overturns early.

There aren’t that many challenges in the first inning, comparatively; the 2.1% overall challenge rate in Triple-A in 2025 was the lowest of any inning, and it only increases incrementally until we hit 3% in the fifth and then nearly 5% in the ninth. That, intuitively, should make sense – in the early innings, the situations usually aren’t important enough to risk losing the ability to challenge later. By the ninth, there’s no tomorrow. Use it or lose it. There’s not much downside to being wrong.

That’s even more stark on the batter side, where the first-inning challenge rate of 3.5% more than doubles to 8% in the ninth. Batters wanted to save it for the biggest spots.

But the success rate, then, is the exact opposite trend, which also makes sense. If you’re going to challenge in the first inning, you better be confident you’ll be right. (Remember: you aren’t given a maximum number of challenges. You’re given the ability to be wrong twice in the first nine innings.) No one wants to be the guy who blows challenges for his team for the rest of the game because of a poorly conceived first-inning challenge.

Interestingly, though: That only worked that way on the fielding side. In the first, the fielding team was correct nearly two-thirds of the time, staying well over 50% until the late innings. But batters stayed consistently in the range of 45% for the first eight innings, before an expected decline in the ninth, when there’s little cost to trying it.

4. Batters care more about avoiding strikeouts than fielders do about avoiding walks.

While Triple-A batters challenged on just under 5% of challengeable pitches (4.8%, to be exact), that skyrocketed to 20% on two strikes, and 25% on full counts.

You can take that to mean that on two strikes, batters were four to five times more likely to use a challenge to avoid the strikeout than on non-strikeout counts – understandably, of course. But there’s a real cost to that: Being more desperate to overturn that strike three meant that Triple-A batters were much, much less effective at being right.

Batter success rate:

• Total: 45%
• Two strikes: 36%
• Full count: 34%
• Other counts: 51%

Interestingly, the fielding side didn’t show quite the same spread. The 2% fielding challenge rate merely doubled on three balls, and went up to 4.8% on full counts.

Why? It’s easy enough to point to the differing value proposition here. Strike three for a batter ends his time up, and guarantees that 25% or 33% of his day, at a minimum, ended in a whiff. For pitchers and catchers, you move on to the next. A walk simply doesn’t hurt them as much as making an out does for the batter.

5. There’s enough of a spread that we expect to see real skill in this.

Again, we can’t say this enough: Minor Leaguers are not Major Leaguers. In the same way that we shouldn’t expect a member of the Oklahoma City Comets or Norfolk Tides to hit like Juan Soto, perhaps they won’t be as good as challenging, either. Just keep that in mind.

But in terms of teams, we saw the Las Vegas Aviators (A’s) be right 54% of the time as batters, with the 30 teams taking small steps down until the 36% of the Syracuse Mets at the bottom – which is a big spread. We saw batters being right 83% of the time, as in Toronto’s Davis Schneider going 10-2 in a brief stint back to the Minors; we saw them being right just 12% of the time, as in Colorado’s Zac Veen going 3-22.

Fielding teams had an even larger gap, with the Louisville Bats (Reds) being correct a whopping 68% of the time, and the Syracuse Mets again at the bottom, merely 44% correct. For the Bats, that was largely about catcher PJ Higgins, who was an incredible 48-14 (77%) on challenges with him behind the plate, while a number of other catchers were more in the 35% range.

(As noted, we don’t know for certain the catcher/pitcher split in Triple-A last year, but it’s safe to assume the catcher initiated most of them.)

So far this spring, San Diego’s Freddy Fermin has been right all four times he’s tried it.

But, since every challenge isn’t created the same, we created a model, grading each opportunity based on pitch location, challenges remaining, situational leverage, and ball/strike/out details. Based on the chances Higgins got, an average catcher would have been expected to challenge 72 times; he did so 62 times. His chances suggest a 39-33 (58%) success rate, and he was 48-14 (77%). The end result is that he was so good at knowing when to challenge and on which pitches and in which situations that he was +28 overturns vs. expected, a whopping number, particularly when the weakest challenger, then-Mariners prospect Harry Ford, was -16.

It’s the same thing on the batting side, too. Schneider, as we said, was right 83% of the time, the highest of any hitter with at least 10 challenges, which was a +7 factoring in pitch location, situation, and all the items listed above. Veen was right just 12% of the time, giving him a -16. There’s skill here. There’s value to be added – or lost.

It matters, too, if used in big spots. In Triple-A last year, 1,239 strikeouts were prevented (at least momentarily) by the batter saying no, that wasn’t strike three. On the other side, 584 walks were stopped (again, for the moment) by the fielding team who correctly claimed it wasn’t ball four. Then, 323 times, you got the perfect marriage of both: a full-count pitch that went directly from a strikeout to a walk, or vice versa, because of a challenge.

“For a hitter who knows the zone, that really is a weapon, right?” Giants baseball boss – and noted excellent former catcher – Buster Posey told the San Francisco Standard a few weeks ago. “I mean, think about a 1-1 count flipping to 1-2, and then reversing to 2-1 with a challenge. It’s a big deal.”

The actual math behind a 1-1 count going from 1-2 to 2-1? Last year in the bigs, batters hit .161 with a .411 OPS on 1-2 counts, and .329 with an .890 OPS on 2-1 counts.

Not a big deal. It’s a huge deal.

6. Yes, framing is still going to matter.

This was a big fear for catchers, many of whom pile up considerable value by saving strikes for their pitchers. But the new system is not going to have as much of an effect as you’d think on them – and some catchers may regain or even exceed any lost value in being good at challenging.

It comes down to a simple numbers game. If 3% of challengeable pitches earn a head-tap, then 97% of them don’t; if approximately 7% of takes on the edges get challenged, then 93% of them don’t. (Again, if those numbers seem low, it’s because so many of those borderline pitches are simply not that obvious, and too risky to challenge, or are in low-leverage situations where it’s not the right time to try it.)

That’s so, so many pitches where receiving is still going to make a huge difference, then. Several Triple-A catchers received over 4,000 non-swings on the edges of the strike zone, and no catcher had more challenges against him than the 91 that Cleveland prospect Kody Huff had.

Besides, a good way to not have to risk a challenge is by getting the calls you want in the first place. If your side is out of challenges, then you, the catcher, would best make sure you’re receiving pitches in a way that they’re called as strikes. If you’re turning borderline pitches into strikes by good receiving, then you’re also goading the batters into making risky challenge calls. There’s so much strategy in here.

7. Do different positions challenge better?

We thought, potentially, that catchers-as-batters would be really good at this. After all, they’re going to have to manage the ABS system on both sides of the ball, unlike other positions, and should in theory have the best command of the strike zone of any position.

As it turns out: That really, really didn’t happen in Triple-A. Catchers challenged the least of any position at the plate, and when they did, they were correct less than any other glove-wearing spot on the field. (Worded carefully, because designated hitters were the least successful.)

It turns out that shortstops, by far, were the best at knowing when to challenge or not. Does it catch your eye that designated hitters, who generally are at DH because they're offering limited defensive value, were the weakest at this? Us, too.

We don’t really have a good answer for this. Could be a fluke of the Minors that won’t repeat in the Majors; could be that the long-held assumption that shortstops are the best athletes on the field plays out in unexpected ways here, too. It’s something to watch in the Majors in 2026, for sure.

8. Are better-framing catchers better at challenging?

OK, so maybe catchers don’t have any obviously superior skill here. What about good catchers? Do those who are excellent receivers have some kind of advantage in challenging? Repeating again that we’re looking at Triple-A catchers and umpires, not Major Leaguers, the answer in 2025 was a resounding: Nope.

There were 121 catchers who issued at least 10 challenges, and also had at least 100 framing opportunities. If this graph looks like a big mess of nothing, with no particular trend, that’s exactly right.

To cherry-pick two extreme examples from Major Leaguers who spent time in the Minors last year: Miami’s Agustín Ramírez and Mets backstop Francisco Alvarez had similar framing stats in the bigs in 2025. But as challengers in Triple-A, Ramírez was right 83% of the time, while Alvarez was correct 46% of the time. That’s independent of leverage, location, and situation; and again, this may not hold true with ABS in the big leagues, but at least in the Minors, good framing didn’t equal good challenging.

9) Did taller or shorter batters do better or worse in challenges?

This, more than anything, is what Yankees fans are dying to know. Did Aaron Judge, all 6-foot-7 of him, face a more difficult zone than other hitters simply because umpires don’t often see a zone that tall?

“He’s one of the most miscalled zones in baseball,” catcher Austin Wells said, “[because] being so tall, he’s getting calls below his knees all the time. That’s tough. It might be harder for him because that’s how he’s been called for so long, but I know he’s going to benefit from it.”

That’s mostly true. However, the focus on Judge dealing with unearned strike calls down low partially obscures that he was also able to get away with unearned ball calls up high. Those at least partially, though not fully, made up for his losses down below.

That said, we didn’t exactly see this play out at Triple-A for tall batters. For one thing, we have another 6-foot-7 Yankees outfielder there in Spencer Jones, who was 10-8 (56%) in his challenges, for +1.2 overturns vs. expected. That’s not a standout number, but it also doesn’t tell us that much by itself, because he’s one batter and we have no idea what his coaches were instructing him to do or not do, ABS-wise.

Instead, let’s break down all of Triple-A into three groups by height.

Challenge success rate, 2025 Triple-A batters

• Short (5-foot-9 or under): 50%
• Medium (5-foot-10 to 6-foot-2): 44%
• Tall (6-foot-3 or higher): 44%

Not much there, is there? You might be pointing out that Judge is on the taller end of the tall range, and that’s true, but even if we looked only at 6-foot-6 and above, that doesn’t change the outcomes at all – though now we’re into only 3% of total challenges, so there’s a real sample size issue there.

Instead, maybe it’s Mookie Betts, Jose Altuve, and the game’s smaller hitters who stand to benefit here. After all, the three most successful challengers in Triple-A last year, by the results of the overturns vs. expected model, were all relatively diminutive – Bryan Torres (5-foot-7), Rafael Lantigua (5-foot-7), and Jamie Westbrook (5-foot-7). Altuve claimed earlier this spring he wasn't planning to use the challenge ability very often. We'll guess that might change quickly.

10. What were the wildest and most important Triple-A challenges?

We thought you’d never ask. Let’s do the fun ones.

Overwhelmingly, challenges look like what you think they do, which is a ball just clipping the edge of the zone – or ever so slightly off of it – that could really go either way.

The funniest challenge, for our money, came in April in the ninth inning of a game in which Atlanta’s Triple-A affiliate was beating Philadelphia’s, 8-4. We say this because at 8 inches away from the nearest edge of the zone, it was the most in-the-zone in-zone pitch any batter challenged. But we also get why Erick Brito did this, too. Down four in the ninth, in a full count, and with a challenge remaining, well, what’s the harm?

Then again, that this came on April 16 and never was topped for the rest of the season might tell you about the ways teams instructed their batters, too.

The most important challenge came a week later, in Toledo. By leverage index, it was a situation nearly 10 times as important as an "average" spot, and the details make clear why. In the bottom of the 13th, Toledo had the bases loaded, down 8-7 to Omaha, with a 3-1 count. It’s about as important as a single pitch can be, other than a full count.

Akil Baddoo’s challenge was strong, turning strike two into a game-tying RBI walk. The kicker: The next batter, Riley Unroe, also walked, giving Toledo a wild 9-8 win.

We're not sure if Major Leaguers will provide us the same kind of entertainment -- but we're pretty excited to see them try.