Robot umpires approved for MLB in 2026 as part of challenge system. ABS will be introduced in the form of a challenge system in which the human umpire makes each call, which can be appealed to the computer. Stadiums are outfitted with cameras that track each pitch and judge whether it crossed home plate within the strike zone. The challenge system adds a wrinkle. While the strike zone actually called by big league umpires tends to be oval in shape, the ABS strike zone is a rectangle, as in the rule book.