ABS challenge system: What we've learned through 3 weeks of MLB play

It has been only three weeks, but Major League Baseball’s ABS challenge system has ushered in a whole new genre of statistics in a sport that was already known for the treasure trove of numbers and data points that help us understand what’s happening on the field. With players now having the option to challenge umpires’ strike-zone judgment — but with just two challenges per game and only successful challenges retained — we have a fascinating, new way to compare teams’ successes, failures and tendencies.

We’re still in the earliest stages of comprehending how the ABS challenge system is best utilized — and so are the teams. Even so, it hasn’t taken long for some intriguing trends to emerge, so here are a few takeaways from what we’ve seen so far.

Which teams have been the best and worst at using the ABS challenge system?

Through three weeks of MLB play, there have been 1,143 challenges issued. Of those, 619 have been successful, meaning players have been right more often than not when challenging an umpire’s ball or strike call, with a 54% overturn rate. But not all teams are succeeding at this clip. Some have been much better, and some have been much worse: Nine clubs have a success rate above 60%, with the Reds comfortably ahead of the pack at a whopping 72%, while three teams — the Braves (39%), Guardians (39%) and Nationals (34%) — fall below 40%.

There’s also a pretty wide range in how often teams are challenging. Cincinnati’s league-best mark comes with only 29 challenges, tied with Washington for third-fewest of any team. Meanwhile, the Twins are tapping their heads all the time, having already challenged 61 calls this season — nine more than the second team, Colorado at 52 — with a 57% overturn rate. This makes basic sense; teams retain challenges if they are correct, and thus can rack up a larger raw total by overturning more calls. On the flip side, it’s been harder for teams such as Washington to challenge more frequently when the Nats have so often been incorrect early in games, thus running out of opportunities to protest calls.

When during games are challenges happening the most?

Before we look at some more team-specific trends, here’s an overview of the game situations in which challenges have been utilized most. Entering the season, it stood to reason that teams would try to save challenges for higher-leverage moments later in games, but so far, that hasn’t really been the case. Here’s a breakdown of challenges by inning:

• 1st inning: 111
• 2nd inning: 101
• 3rd inning: 111
• 4th inning: 103
• 5th inning: 118
• 6th inning: 138
• 7th inning: 159
• 8th inning: 148
• 9th inning: 138
• Extras: 16

Among this sample, there is a slight lean toward the later frames, but so far — whether or not teams are explicitly green-lighting this behavior — players have been happily tapping their heads early in games.

Which hitters have yet to challenge?

So far this season, 252 batters have challenged at least one called strike. But there are some holdouts who haven’t tried MLB’s new toy, for whatever reason. Here are the hitters who have seen the most called strikes without issuing a single challenge:

1. Chase Meidroth: 77 strikes
2. Brice Turang: 68
3. José Ramírez: 63
4. Masyn Winn: 60
5. Mike Yastrzemski: 58
   T-6. Matt McLain: 57
   T-6. TJ Friedl: 57
   T-6. Jung Hoo Lee: 57
6. Will Smith: 56
   T-10. Francisco Lindor: 54
   T-10. Drake Baldwin: 54

This is not to say these players saw many horrific calls by the umpires that deserved to be protested. And perhaps there have been times when they would’ve liked to challenge, but their teams didn’t have any left. At the same time, it’s not hard to watch some of the called strikes for these hitters and wonder: What are you waiting for?!

Still, we can be patient as hitters around the league settle into the new system. And having two catchers on this leaderboard makes sense; Smith and Baldwin would probably rather save their challenges for when they’re behind the dish. As for the rest of this group, it’ll be interesting to track how long some of these guys go without challenging and whether this is merely early-season hesitation or a conscious choice to neglect their new privilege.

Are teams preferring to challenge more while batting or while pitching?

Of the challenges issued, 611 (53%) have been by the fielding team (with the vast majority of those issued by catchers) and 532 (47%) by the batting team. But certain teams have demonstrated more significant splits. Here’s a breakdown of which teams’ challenges have leaned most heavily toward one side of the ball:

Highest percentage of challenges on defense:

1. Dodgers: 73% (24 of 33 challenges issued while pitching)
2. White Sox: 72% (31 of 43)
3. Marlins: 71% (35 of 49)
4. D-backs: 66% (21 of 32)
5. Brewers: 65% (28 of 43)

Highest percentage of challenges on offense:

1. Tigers: 64% (25 of 39 challenges issued while batting)
2. Yankees: 63% (29 of 46)
3. Orioles: 59% (22 of 37)
4. Guardians: 58% (21 of 36)
5. Blue Jays: 57% (21 of 37)

This is one indicator of teams’ strategic preferences that’ll be worth monitoring as the season unfolds. It stands to reason that if overturn rates continue to heavily favor catchers, as they have at every interval leading up to the challenge system’s introduction, teams would move toward saving their challenges for the purposes of run prevention on the mound, rather than rally preservation at the plate. But there’s also value in being able to keep an inning alive on offense with a well-used challenge late in games, so don’t expect clubs to completely abandon that option anytime soon. There is an ideal balance that all the teams are still searching for. — Shusterman

The Dodgers have the most obvious plan

No team has tapped less often on offense than the two-time defending champs. Entering play Friday, Dodgers hitters had used just nine challenges, two fewer than any other club and 22 behind the league-leading Twins. For a team that does nothing by accident, well, this can’t be an accident.

Los Angeles’ strategy appears to revolve around reserving its challenges for its catchers. Will Smith, the club’s every-day backstop, has issued the fourth-most challenges (21) of any catcher in the league. On a rate basis, Smith has been just OK; his 62% overturn rate is right around average for catchers. But he’s letting it fly, in part because he almost always has a challenge or two in the chamber.

Things get even more interesting when you break down when exactly Dodgers hitters have deployed their challenges. Of their nine taps, seven came in the seventh inning or later (77%). That’s a stark contrast to the rest of the league; which is using just 39.7% of its challenges in those frames.

The two exceptions to this Dodgers rule? One was an awful, easily overturned, strike-three call on Alex Call in a game Los Angeles was leading by five runs in the third inning. The other was a bizarre, emotionally charged, early-game mistake challenge by Hyeseong Kim. L.A.’s young utility infielder clearly regretted his decision immediately, staring off toward his dugout with a guilty look on his face. Moral of the story: If you’re a hitter and you end up on the Dodgers, probably don’t challenge unless you absolutely have to.

The Red Sox aren’t challenging

Boston is dead-stinkin’-last in MLB in both attempted and successful challenges. That hesitancy has been particularly striking on the defensive side; Red Sox catchers have challenged only nine times. Every other club is in double digits.

Notably, Boston’s backstop tandem of Carlos Narvaez and Connor Wong has gotten more passive over time. They tapped five times in the club’s first four games but have tapped just four times in April thus far. By contrast, White Sox backstop Edgar Quero challenged five times against Tampa Bay on Thursday alone.

So why are the Red Sox so skittish? It’s tough to say. Their lack of hitter challenges (11, tied for second-last) feels like a small-sample size mirage, something that should even out over the long haul.

But the hands-off approach behind the dish feels like something bigger. Could it be related to Narvaez’s disciplinary benching on April 1, the day the Sox reduced their challenge rate? Narvaez catches the bulk of Boston’s games, so maybe this is more about him than it is about a grander strategy. Either way, the Red Sox declining to engage with ABS feels like a mistake.

How bad at challenging are the pitchers, really?

Probably bad, but it’s hard to be certain because they’re hardly ever challenging: Thus far, pitchers are 11-for-22.

Minor-league and spring training data told us that pitchers, for a number of reasons, aren’t good at this. The numbers are a bit hazy, but the overturn rate for hurlers was around 41%. That’s because most hurlers end up in a poor physical position to actually see the ball cross the plate. More importantly, they’re emotionally invested in each particular pitch in a way that makes it impossible for them to view the umpire’s call objectively.

Accordingly, a handful of teams admitted that they would heavily discourage their pitchers from challenging. And that has played out in the data. Thirteen teams have yet to use a single pitcher challenge. Only three teams — Baltimore, Pittsburgh and Philadelphia — have had multiple pitchers challenge. No single pitcher has challenged twice.

The higher-than-expected 50% success rate for pitchers is likely a product of small-sample size. But it might also be a sign that some pitchers are challenging only blatantly obvious misses.

Walks are up this season — is ABS the reason?

Pitchers are giving away free passes right now like it’s an episode of Oprah. The league-wide walk rate entering play Thursday was 9.9%, nearly a full point higher than it was during March/April 2025. This is notable; the league-wide walk rate hasn’t finished above 9.0% in a full season since 2000.

Is ABS to blame? It’s complicated — more balls are being challenged into strikes than strikes into balls, for instance — but it’s certainly part of the story.

The most telling nugget is that walk rates rose in the minor leagues after ABS was implemented. Something similar is probably happening in the bigs right now. A dive into the data shows that the top of the zone, in particular, has become less fruitful for hurlers. Remember, the new zone is the same horizontally as the old zone (the width of the plate), but it changed vertically (now it’s according to player height).

That generally means a lower top rail, giving pitchers less leeway at the letters. Considering how much emphasis in recent years has been placed on peppering elevated fastballs, this trend of more walks shouldn’t come as a huge shock. Our guess is that MLB wants pitchers to gradually adjust how they pitch; more balls in the zone, fewer high-effort high heaters, more balls in play, more action, etc. What we’re seeing now, in the early going of this new era, are growing pains. We expect that teams and pitchers will react to this shift, understand they now have a smaller box to throw in and adapt accordingly. For now, though, walks are plentiful. — Mintz