Major League Baseball is expanding its automated strike zone experiment to Triple-A, the highest level of the minor leagues, this season.

The independent Atlantic League became the first American professional league to let a computer call balls and strikes at its All-Star Game in July 2019.

The system also was used in the Arizona Fall League for top prospects in 2019, drawing complaints of its calls on breaking balls.

The Major League Baseball Umpires Association agreed in its labor contract that started in 2020 to cooperate and assist if Rob Manfred decides to use the system at the Major League level.