A comprehensive dive into what we've learned so far from ABS challenges

During the Mariners’ opening series against the Guardians, television analyst and former MLB pitcher Ryan Rowland-Smith noticed something telling about the new challenge system: hitters hesitated. They often seemingly wanted to tap their helmets and challenge a borderline call, but they mostly held back.

They had good reason to pause. Players now face a real-time calculus on every pitch, challenges are a scarce resource, and many borderline calls and situations make decisions far from obvious. After two seconds, the window to challenge closes.

Baseball’s new Automated Ball-Strike (ABS) Challenge system has already won over fans. It delivers more accurate calls and adds an entertaining layer of strategy and umpire-versus-player theater. With only two incorrect challenges allowed per game, teams must decide not only when to challenge but who should do it. Often that means a player putting the team first.

How can teams optimize the challenge system? How are players stacking up through the first week of the 2026 season? Let's explore:

Count leverage comes first

The marginal expected run-value difference between counts is massive.

For example, a full count carries a .730 swing in run expectancy as a single pitch yields either a baserunner or an out. By comparison, the difference between a ball and a strike on the first pitch is a mere .07 run value.

Batters and catchers have always understood the general value of counts. Now they must zero in on the specifics.

Early results are mixed.

The highest number of challenges (27) by count have come on even, 2-2 counts through one week, which is the second most valuable count in terms of an expected run value swing (.445). This is quality real-time calculation by players.

But the 0-0 counts rank second (25), even with some front offices instructing their players never to challenge in that count.

Yes, there are far more 0-0 counts since that's the state in which every plate appearance begins, and teams retain their challenge if it's successful. But batters and catchers should be waiting for deeper counts before tapping a helmet.

There have been 19 challenges on full counts, which ranks fourth. There should be additional full-count challenges and perhaps there will be more.

A larger sample of past Minor League play suggests this will change, as only 1.6 percent of first pitches were challenged compared to 8 percent of full-count calls.

Game leverage trumps everything

The single biggest factor in determining when to challenge is the expected change in win probability. A borderline pitch in a high-leverage moment – like a situation with the tying run on second with two outs in the ninth, or bases loaded and tied in the sixth – justifies an early-count challenge.

Thus far, 54 percent of challenges have come within the sixth inning or later, innings that have covered just 44 percent of game time but generally contain higher-leverage moments.

Players have challenged more often during periods of the game with greater leverage but it’s still probably not enough, as MLB.com’s Mike Petriello argued the other day. Out of curiosity, I asked Google’s Gemini about optimal challenges by innings. The AI tool suggested 70 percent of challenges should be reserved for the sixth inning and later.

So players are in the ballpark, but like with counts, challenging is not quite being optimized.

Fewer challenges should be made early. Athletics catcher Austin Wynns presumably would like to have his second-inning challenge of a 1-0 ball call back from Wednesday in Atlanta. That's not optimal.

Even though he lost it, Matt Wallner's challenge of a two-out, full-count pitch with a runner on base in the first inning on Wednesday was more defensible.

Who should challenge?

Only pitchers, catchers and batters can initiate challenges. And baseball has learned quickly who should – and who should not.

Pitchers have the lowest success rates. They stand farther from the strike zone, and they may carry more bias toward calls that would help them escape jams or extend outings. Teams are instructing pitchers to practice restraint and let catchers decide – but that's not always easy.

In the fourth inning on Wednesday night, Twins pitcher Joe Ryan froze with his arms in the air following a close 2-2 pitch that was called a ball just off the plate. He wanted to challenge but restrained himself. Twins catcher Ryan Jeffers opted (correctly) to not challenge.

Earlier in the day, George Kirby challenged a call, and did so successfully – though he went against some of our aforementioned rules as it was also a first-inning challenge.

During MLB's 288-game experiment with ABS last spring, pitchers only had a 41 percent success rate overturning calls. Hitters stood at 50 percent, while catchers enjoyed a 56 percent success rate. And there's clear logic why catchers should be the most effective: they have the best view of the zone and see the most pitches during a game and over the course of a season.

Early on, catchers have been more successful with a 58 percent win rate compared to 55 percent for hitters.

Catchers should be challenging even more often as their total challenges (180 through April 1) are 10.5 challenges below Baseball Savant's expected challenge metric. The Yankees' Austin Wells is a perfect 4-for-4 in challenging calls entering the weekend. Salvador Perez leads MLB with five overturns (71 percent success rate).

When hitters challenge, teams ideally want their best sluggers getting the benefit of overturned calls.

Entering the weekend, 55 of the 82 batters (67 percent) to challenge were above-average hitters in terms of wRC+ last season (minimum 200 plate appearances). Overall, the average hitter to challenge this season averaged a 112 wRC+ last year, meaning they were 12 percent better than the league-average hitter.

That tells us batters are generally making team-first decisions.

Ideally, those hitters also possess strong strike-zone discipline rather than free-swinging approaches.

The only time to deviate is game context. A weak-hitting ninth-place batter should challenge a two-strike call with one out and a runner on in a late, close game.

It's a lot to consider; perhaps we could all benefit from a quarterback-style wrist band informing when to (and when not to) challenge:

• Pitchers should never challenge
• Early-inning challenges should be rare and tied to a high-leverage situation (runners on, two outs, etc.)
• Early-count challenges should be extremely rare and only happen in high-leverage situations
• A team should never enter the late innings without at least one challenge
• Catchers should challenge calls more often. (They have the highest success rates)
• The overwhelming amount of challenges from hitters should be from those who are above-average producers, and ideally with strong batting eyes

There are many inputs that go into the decision. Players are generally within the ballpark in making correct, team-first decisions thus far, but there is still room for improvement. Ultimately the teams and players that calibrate the fastest will have an edge – the newest edge in the game.