Ethics CasesSport

Cases · Major League Baseball · 2019–2026

Robot Umpires: MLB's Automated Ball-Strike Challenge System

Baseball has long relied on umpires' judgment to call balls and strikes. After testing automated ball-strike (ABS) systems in independent and minor leagues since 2019, MLB's competition committee approved a challenge system for 2026: umpires still call pitches, but each team gets two challenges per game to have a call reviewed by tracking technology. Successful challenges are retained. The system defines the strike zone using each batter's height. Supporters say it improves accuracy; critics worry about the loss of skills like catcher framing and the human element. The case raises questions about technology, fairness, tradition and the role of officials.

By Tanner Simkins, editor

Timeline

  1. The independent Atlantic League first uses ABS in its All-Star Game.
  2. ABS is tested in Triple-A.
  3. ABS is used across all of Triple-A.
  4. The challenge system is tested in MLB spring training and the All-Star Game.
  5. MLB's competition committee approves the challenge system for 2026.
  6. Ten calls are overturned in a postseason game, a nine-inning MLB record.

The ethical issues

  • Accuracy versus human judgment.
  • Fairness: a strike zone based on height.
  • Labor: the role of umpires.
  • Tradition and skills like catcher framing.
  • Governance: who decides rule changes.

Stakeholders

StakeholderInterests & obligations
PlayersFair calls and the value of their skills.
UmpiresTheir role and authority.
MLBAccuracy, pace and fan interest.
FansFairness and entertainment.
TeamsStrategy and competitive balance.
Technology providersReliability.

The case

Baseball’s strike zone is defined in the rulebook, but for over a century umpires have called pitches by judgment. Players and fans have long complained about inconsistent zones.[1]

Background

The choice of a challenge system, not full automation, reflected opinion inside and outside the game. In a 2024 MLB poll, 61% of team personnel, including players, and 47% of fans preferred a challenge system. Some 28% of team personnel and 30% of fans wanted no ABS at all, and 11% and 23% respectively wanted full automation.[1] Triple-A results informed the design. In 2024, Triple-A teams in six-game series used full automation for three games and challenges for three. From June 25 that year, MLB used only the challenge format, and 51% of Triple-A challenges were successful that season.[1]

Using height to set the zone had a side effect. MLB began measuring players precisely in 2026, without team staff involved. Of 430 hitters on Opening Day rosters, 225 had listed heights at least an inch shorter than in 2024 or 2025.[1]

The rules and governance

The challenge rules are part of MLB’s playing rules, approved by the Joint Competition Committee, a body that gives players and an umpire a formal voice alongside owners.[2] Human umpires remain the first decision-makers. ABS decides only when a player challenges, and then umpires must apply its call. As with any ball-strike call, players can still be ejected for arguing.[1]

The measurement standard is stricter than the one used to grade umpires. MLB’s internal evaluations of umpire accuracy use a buffer zone at the edges of the strike zone where calls are not counted against umpires because of measurement uncertainty. ABS has no buffer zone.[1] MLB officials told The Athletic they had 95% confidence that ABS reports a pitch’s location within a small margin, and some retired umpires have questioned its accuracy.[1]

Testing

The independent Atlantic League first used an automated system, nicknamed “robot umpires,” at its 2019 All-Star Game; umpires received calls through earpieces.[1] The Single-A Florida State League has used ABS since 2021.[2] The Arizona Fall League also used it in 2021, drawing complaints that breaking balls were called strikes even when they dropped out of the zone.[1] MLB tested ABS in Triple-A from 2022 and across all of Triple-A from 2023, trying both fully automated calls and a challenge format.[1][2] The challenge system debuted in MLB spring training in 2025 and at the 2025 All-Star Game.[2]

MLB experimented with the zone’s dimensions. Its width was reduced from 19 to 17 inches, the width of home plate, and the top and bottom are set as percentages of each batter’s height, with the top raised after pitchers complained.[1]

The decision

On September 23, 2025, MLB’s Joint Competition Committee approved the ABS challenge system for 2026.[2] The committee was created under the collective bargaining agreement and has six owners, four active players and one active umpire, so owners hold a majority.[2][6] The vote was reported as 9–2. All six owners and three of the four players voted in favor, and one player and the umpire voted against.[5]

Under the rules, human umpires still call every pitch. Each team starts with two challenges and keeps any that succeed. Only the pitcher, catcher or batter may challenge, and he must do so immediately, by tapping his cap or helmet and saying so, without help from coaches or teammates. A team with no challenges left gets one in each extra inning.[2][3] Twelve Hawk-Eye cameras track each pitch. A pitch is a strike if any part of the ball touches a two-dimensional zone 17 inches wide, with its top at 53.5% of the batter’s height and its bottom at 27%. Independent testers measure the players. The umpire announces the result, a graphic appears on the scoreboard and broadcast, and the process takes about 15 seconds.[2]

MLB framed the choice as a compromise. Commissioner Rob Manfred said players’ “strong preference… for the Challenge format over using the technology to call every pitch was a key factor.” He praised the committee for “preserving the integral role of the umpire in the game with the ability to correct a missed call in a high-leverage situation.”[2] Committee chairman John Stanton, the Seattle Mariners’ chairman, said the system kept “the human element of the game” while adding “a new fan-friendly engagement moment.”[2] In 2025 spring training, teams challenged just over four pitches a game, with success near 50%. Catchers overturned 56% of their challenges, hitters 50% and pitchers 41%.[2]

The first season

MLB has said the system’s measurements are highly precise, though some players have expressed concerns about its margin of error.[1] In the 2026 regular season, teams made 10,557 challenges, an average of 4.35 a game, and 54% of challenged calls were overturned.[4] Catchers succeeded on 59% of their challenges, batters on 49% and pitchers, who rarely challenged, on 40%.[1][4] Team success rates ranged from 62% for Cincinnati to 47% for Pittsburgh. Some players simply declined to use the system. One veteran hitter went 686 plate appearances without a challenge.[4]

Managers described a new skill. “It’s like a new muscle for players to learn,” Yankees manager Aaron Boone said, calling it “a new instinct of knowing when to challenge.” Houston manager Joe Espada said ABS had changed “how more selective some of these lineups are” and forced pitchers “to be more aggressive in the zone.”[4] Players have observed that catchers can no longer frame pitches to win strike calls outside the zone.[1]

Aftermath

The challenge system reached the postseason in its first year. A catcher’s successful challenge ended Game 2 of the 2026 National League Wild Card Series, the first game-ending ABS challenge in postseason history.[4] On October 4, 2026, ten ball-strike calls were overturned on challenges in a postseason game, a record for a nine-inning MLB game.[1] The first challenge in an MLB All-Star Game, in 2025, was a catcher’s successful challenge that resulted in a called third strike.[1] Mexico’s top league adopted a similar challenge process for part of its 2026 season.[1]

The core dilemma

Accurate calls make the game fairer. But umpires’ judgment, players’ skills in influencing it and arguments over calls are part of baseball’s culture. A challenge system seeks a middle path. Is it the right balance, and what values should guide officiating technology?

Competing values

  • Accuracy vs. tradition.
  • Technology vs. human roles.
  • Uniform rules vs. individual bodies.
  • Efficiency vs. drama.

Strongest arguments

For ABS challenges: it corrects clear errors that affect outcomes while keeping umpires on the field and limiting delays.

Against or for caution: it devalues skills such as framing, publicly exposes umpires, and relies on a zone defined by height formulas and measurement margins.

Applying the frameworks

Utilitarian

Consequentialists weigh accuracy, fewer disputes and fairer outcomes against costs: losing catchers’ framing skill, possible measurement error, longer games and the pressure on umpires. A challenge system tries to capture most of the accuracy benefit while keeping the human element that many fans value.

Kantian (duty)

A Kantian lens asks what fairness to players requires: if a rule defines the strike zone, players have a claim to have it applied as written. It also asks whether players are treated fairly when a system without a buffer zone judges calls that umpires were trained to make with one.

Virtue

Virtue ethics asks how technology changes the excellences of the game. Framing was a valued catching skill; challenging well now requires judgment and nerve. It also asks how umpires keep their authority and professional pride when their calls are regularly overturned in public.

Walk it through: the Simple Decision Model

  1. Spot the issue. You are a member of MLB’s Joint Competition Committee in September 2025, voting on ABS for 2026. The stakeholders include players, umpires, owners, fans, broadcasters and amateur leagues that follow MLB’s lead. The codes in play are the playing rules, the collective bargaining agreement and the umpires’ labor agreement.
  2. Gather facts. What do the Triple-A data show about accuracy, game length and player experience? What are the measurement limits?
  3. Test options. Options: (a) keep human umpires only; (b) adopt the challenge system; (c) adopt full automation. Weigh accuracy against tradition, skill and the role of umpires.
  4. Check codes and law. Are commercial considerations, such as broadcast graphics, driving the choice? Are umpires’ concerns being considered fairly?
  5. Decide and document. Record the vote and the reasons.
  6. Communicate and follow up. Communicate the rules clearly to players, umpires and fans, and commit to reviewing data after the first season.

What’s settled and what’s contested

  • Settled: the system’s adoption and rules.
  • Contested: whether full automation should follow; the effect on umpires and players.

Why this case matters

ABS is one of the most significant changes to officiating in a major sport and a test case for how technology reshapes judgment in competition.

Key terms

Trust
The public’s belief that what they are watching is real. Integrity failures are ultimately failures of trust.
Integrity
A commitment to honesty and ethical principle in competition and administration, including when nobody is watching.
Stakeholders
Everyone with something at stake in a decision: athletes, coaches, parents, officials, fans, employees, sponsors, media, communities and regulators, including the less visible ones.
Rules vs. spirit of the game
Rules are the written minimum; the spirit is the fairness and respect the rules exist to protect. Rules set the floor; spirit sets the ceiling.

Definitions from the Ethics Cases glossary.

Discussion questions

  1. Is the human umpire's judgment part of what makes baseball valuable?
  2. Should all pitches be called automatically rather than by challenge?
  3. Is a height-based strike zone fair?
  4. What happens to skills like catcher framing, and does that matter?
  5. How accurate must technology be before it replaces human judgment?

Sources

  1. Automated Ball-Strike System — Wikipedia
  2. Press release: MLB announces ABS Challenge System coming to the Major Leagues beginning in the 2026 season — MLB.com
  3. Robot umpires approved for MLB in 2026 as part of challenge system — AP News
  4. Robot umpires flip 54% of challenged calls in ABS debut as teams learn to time appeals (AP, Oct. 2, 2026) — Associated Press (via WDIV ClickOnDetroit)
  5. MLB Competition Committee Approves Automated Ball-Strike System For 2026 Season (Sept. 23, 2025) — MLB Trade Rumors
  6. MLB officially beginning Robot Umpires era — ABS approved for 2026 (Sept. 23, 2025) — New York Post