As tracking systems reshape officiating in baseball, soccer and tennis, the real test is whether the rules governing challenges, reviews and explanations can keep pace with the technology.
With two Braves on base and the Phillies leading 4-3 in the 10th inning on Sept. 30, catcher J.T. Realmuto tapped his helmet to challenge a ball call on a 0-2 pitch. Camera tracking showed that the pitch had clipped the strike zone. The call was overturned, the batter was out, and the game ended
Optical tracking of this kind also calls lines at Wimbledon and underpins offside decisions at the World Cup. Yet the three sports have taken different approaches to letting machines influence the result. Baseball gives players a limited number of challenges. Soccer combines tracking with video officials. Tennis has largely handed line calls to an automated system. The difference is not simply technological. It is written into the rulebook.
Cameras and sensors can establish where a ball crossed the plate, where a player stood when it was kicked or whether a boot made contact. But measurement does not always settle the decision.
At the World Cup, a sensor in the ball registered a slight touch by Croatia’s Igor Matanović, putting a teammate offside and erasing a late equalizer against Portugal. Meaning is a separate question: the ball then deflected off a Portuguese defender, and officials had to judge whether that touch was deliberate, since only a deliberate play resets offside. They ruled it was not.
As measurement becomes routine, the design question shifts to authority: who may trigger a check, who makes the final call and how much of the process fans see. Each answer puts a different cost on someone, which is why similar technology yields different contests.
The strike zone becomes a strategy
Baseball kept human umpires and added a rationed appeal: a batter, pitcher or catcher may challenge a ball-or-strike call, and each team begins with two challenges, keeping one when it wins. Scarcity forces players to weigh each pitch: Major League Baseball (MLB) data cited by Forbes show 39.1% of challenges came from the seventh inning on, against 28.6% in the first three. It also means a 52.2% overturn rate in 2025 spring training describes chosen pitches, not umpire accuracy.
MLB stopped short of full automation. Its minor league tests produced more walks and longer games, and full automation would have ended pitch framing, the league said; challenges added about 57 seconds a game in spring training.
The choice came despite 69% of surveyed spring training fans favoring full automation. For MLB, the question is how much control to hand technology without removing the strategy and human elements that shape the game.
Soccer and tennis take different routes
Soccer, where play rarely stops, prioritized speed: FIFA said clear offsides would go straight to on-pitch officials rather than the video referee, with humans keeping the final call and 3D avatars sharpening replays for viewers. The system’s work also shows its failures: when an outage kept the offside graphic from generating before a penalty in Switzerland’s match against Qatar, FIFA said the video officials' lines showed no offside, but released images only about 4½ hours later, ESPN reported.
Wimbledon went furthest, removing the human line call at its 2025 Championships. Hawk-Eye Live, tracking the ball with 18 cameras, replaced about 300-line judges with roughly 80 match assistants kept in reserve. Human error did not disappear; it moved. In a fourth-round match, an operator deactivated the system in error for one game, three calls went unregistered, and the chair umpire ordered a point replayed. Wimbledon apologized, called it human error and removed operators’ ability to switch the tracking off.
What the rulebook decides
The three approaches, therefore, trade one benefit for another cost. Baseball gains strategy and keeps the catcher’s framing craft but adds pauses; soccer gains speed but still depends on human judgment and exposes its system’s failures; tennis gains consistency but depends on the people operating it. The failures show where risk now sits: with the people who operate and govern the system.
In each case, technology changes where the risk sits rather than eliminating it. MLB’s published rules specify the fallback for an untracked pitch: the call stands and the team keeps its challenge.
That is also the lesson for businesses adopting automated decision-making. Who can request a review? Who has the final say? Can customers see how a decision was reached? And what happens when the system fails?
These systems make results more likely to reflect play, and 72% of fans in MLB’s spring training survey said the challenge system improved their experience, though the league ran the survey. What turned Realmuto’s challenge into a decision rather than a measurement was baseball’s rule that someone must choose to ask. Accuracy put the technology on the field; the rules around it decide whether fans see fairness, drama, or simply automation.
