BRIDGEWATER, N.J.—Facing a 3-2 count in the seventh inning here Friday night, T.J. Rivera of the Long Island Ducks let a borderline changeup pass by, tossed his bat away and jogged toward first base. He thought he had drawn a walk to break up a perfect game by opposing pitcher Rick Teasley of the Somerset Patriots.

Five steps down the line, Rivera heard home plate umpire J.B. Torres deliver those two dreaded words: strike three. Rivera glared back at Torres, preparing to plead his case, when he remembered an important detail: Torres didn’t actually make the call. A little voice in Torres’s head told him to do it.

“[Rivera] said to me, ‘I was trying to get that walk, but I forgot it’s not on you tonight—it’s on the computer,’” Torres said.

Baseball’s future has arrived in the Atlantic League, a collection of eight independent professional teams that span from New Britain, Conn., to Sugar Land, Texas. In February, the Atlantic League reached a three-year agreement to audition a series of experimental rules for Major League Baseball to evaluate, largely designed to improve pace of play and generate action. These include the prohibition of mound visits and defensive shifts, shorter inning breaks and enabling hitters to “steal” first base on any pitch not successfully caught in the air.

But last week marked the introduction of the most significant innovation: an automated strike zone, shifting responsibility for calling balls and strikes from a person to an emotionless piece of technology free of the biases and inconsistencies of mere humans. And if the test goes well, the days of big-league players imploring umps to schedule an eye exam could soon come to an end.