The new computerized system is being tested during spring training, leading to a series of challenges from players who don’t know the strike zone quite as well as they think.

A computerized system that calls balls and strikes is being tested during Major League Baseball spring training exhibition games starting Thursday after four years of experiments in the minor leagues.

If there’s one thing baseball fans are averse to, it’s change. Over the MLB’s 149-year history, alterations to the game’s rules, like lowering the pitcher’s mound (1968) or introducing instant replay challenges (2014) came only after years of heated debate between reformers and purists.