They’re the two words that herald the coming of spring, the promise of warm sunshine and long days, the sound of bat-on-ball and the return of the boys of summer: Play ball!

Beginning Thursday, the automated ball and strike system will allow players to challenge umpires’ calls. If all goes well, the system could debut in regular season games as soon as next year.

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.