The Automated Ball-Strike (ABS) system is MLB’s challenge system for ball and strike calls, introduced in 2026. Players can challenge an umpire’s call, and the ABS system — using Hawk-Eye tracking technology — determines whether the pitch was actually in the strike zone.

Each team gets a limited number of challenges per game, similar to replay challenges for other plays. Batters, pitchers, and catchers can all initiate challenges. If the ABS system agrees with the challenger, the call is overturned; if not, the original call stands and the team loses a challenge.

Baseball Nut tracks ABS challenges on every team page, showing total challenges, wins, losses, and win percentage. The Stats page lets you compare ABS challenge performance across all 30 teams. Some teams and catchers are significantly better at picking which pitches to challenge — a new strategic edge in the game.

What is a good ABS?

ABS challenges don’t directly factor into NUT Score, but they affect game outcomes. A successful challenge can turn a strikeout into a continued at-bat or a walk into a strike — changing the plate appearances and outcomes that NUT measures.

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