Major League Baseball is accelerating its technology revolution, moving robot umpire tests for checked swings to the highest minor league level while introducing a suite of rule changes aimed at standardizing controversial calls and speeding up a game that has seen its pace slip.
Major League Baseball is betting big on technology to solve baseball’s most persistent points of contention. In a memorandum to clubs last week, MLB vice president of on-field strategy Joe Martinez announced that the experiment allowing challenges to checked swing calls—a frontier of the sport’s robot umpire initiative—will expand from Class A to the Triple-A Pacific Coast League starting May 5, alongside the existing test in the Florida State League[AP].
This isn’t an isolated tweak. The memo outlines a multi-pronged experiment package also hitting Triple-A, including physically moving second base entirely into the infield (reducing the base-to-base distance by nine inches), slashing permissible pitcher disengagements from the rubber from two to one per plate appearance, and implementing stricter limits on batter timeouts and PitchCom-related issues. Even starting pitchers in the lowest minor leagues will get a chance to re-enter games after removal—a development-focused test not expected for the majors[AP].
To understand this leap, rewind to 2019. That’s when MLB first launched its Automated Ball-Strike System (ABS), the so-called robot umpire, in the minors[AP]. The system uses Doppler radar and motion sensors to track pitches, providing a definitive strike zone. Human umpires still call balls and strikes but can be challenged by teams, each granted two unsuccessful appeals per game with successful challenges retained. The goal was always to improve accuracy, and the data showed promise.
The checked swing challenge is the next evolution. For decades, whether a batter swung or not was a purely subjective call by the home plate umpire, with only a vague rule: “A strike is a legal pitch when so called by the umpire, which is struck at by the batter and is missed.” Since 1976, managers could only request help on “half swings” when the pitch was called a ball. Now, under the test, a swing is objectively defined: it occurs if “the maximum angle between the bat head and the bat handle exceeds 45 degrees.”
Why move this test to Triple-A now? The results from its inaugural Class A run were compelling. Martinez noted that the strikeout rate dropped by 3% during last year’s testing—a significant figure that hints at the technology’s power to correct overzealous strike calls that may have inflated whiff rates. For players and agents, this translates to potentially fairer at-bats and more accurate performance metrics. For umpires, it removes a lightning-rod decision from their plate. For fans, it promises fewer heated arguments over a “check swing” that looks different from every angle in the ballpark.
TheChecked swing test began on May 20, 2025, in the Class A Florida State League and was later extended to the Arizona Fall League. Its expansion to Triple-A is the final proving ground before a potential MLB debut. Triple-A is where the competition is fiercest and most representative of the big leagues, making it the ideal environment to stress-test the system’s speed, accuracy, and integration before a full rollout.
But ABS for ball-strike calls is just one thread in a broader tapestry of change. The other experiments reveal MLB’s dual priorities: increase offense (or at least baserunning action) and decrease dead time. The decision to move second base so it sits entirely within the infield—centered on the existing spot but with a different orientation—directly follows the 2023 enlargement of bases from 15 to 18 inches. That prior change shaved 4.5 inches off the distance between bases, fueling a stolen base surge as the math of the steal became more favorable[AP]. Now, by moving the bag itself, MLB aims to further encourage aggressive baserunning.
The pitch clock, introduced in 2023 to combat interminable games, is also being fine-tuned. Citing a slight increase in average nine-inning game time (from 2:36 in 2024 to 2:38 last year) and a dip in stolen base attempt success rate (from 80.2% to 77.8%), MLB will test stricter enforcement. At Triple-A, teams will get a mound visit for any PitchCom malfunction, and if out of visits, an automatic ball is assessed. Clock stoppages for catcher signal-giving will be eliminated, and non-pitcher personnel must vacate the mound before the visit clock expires.在高阶A级，垒上无人的情况下击球员将不能要暂停；在A级，则完全不允许暂停，除非涉及触身球、潜在受伤或装备问题。双A级将投手离板次数从两次减至一次。
For the fanbase, these changes live at the intersection of excitement and skepticism. The “robot umpire” debate has raged for years—purists decry the loss of the human element and the unique strike zone “framing” art, while progressives welcome any tool that removes egregious errors. The checked swing rule has been particularly maddening; one fan’s clear swing is another’s check. An objective 45-degree threshold could end decades of manager arguments. Similarly, the base-moving experiment is a direct response to the analytics-driven game where teams optimized for home runs over speed. Fans who miss the stolen base era may welcome it, while others might see it as gimmicky.
This moment is about more than rules; it’s about baseball’s identity. The sport is consciously engineering itself for a new audience with shorter attention spans, using technology to impose consistency. The expansion of checked swing review to Triple-A is the most tangible sign yet that the robot umpire is no longer a fringe experiment—it’s on the cusp of The Show. When the 2026 season begins, the “Automated Ball-Strike Challenge System” will be live in the majors[AP]. This Triple-A test is the final dress rehearsal.
The rule changes collectively form a grand experiment to recalibrate the sport’s rhythm. By shrinking the basepaths, limiting pitcher disengagements, and cracking down on clock stoppages, MLB is tilting the scales toward action and against deliberate stalling. The allowance for starting pitchers to re-enter games in the complex leagues is a fascinating outlier—a nod to player development and workload management that may never reach the majors but could inform future pitch count strategies.
As these tests unfold in Triple-A, every called third strike, every close play at second, every mound visit will be data points. The outcomes will determine whether 2027 sees a fully automated strike zone with checked swing review, permanently shifted bases, and a radically streamlined pace. For now, the message from MLB is clear: the era of tinkering is over; the era of implementation is here. The robots are no longer coming—they’re moving up.
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