The independent Atlantic League is so happy with "robot umpires" that it will continue using the system for the rest of the season, starting Thursday.
The league became the first American professional baseball league to let a computer call balls and strikes at its All-Star Game earlier this month. Plate umpire Brian deBrauwere wore an earpiece connected to an iPhone in his pocket and relayed the call upon receiving it from a TrackMan computer system that uses Doppler radar.
He crouched in his normal position behind the catcher and signaled balls and strikes.
"This is a landmark day for the Atlantic League and professional baseball," Atlantic League president Rick White said in a statement. "After successfully unveiling the ABS (Automated Ball-Strike System) at our All-Star Game in York, Pa., and following positive feedback from managers, players, umpires and fans, we are eager to implement the consistent strike zone accuracy offered by ABS technology."
After the All-Star Game, the league started rolling out the technology to stadiums throughout the league.
The umpires have the ability to override the computer, which could consider a pitch a strike when the ball bounces and then crosses the zone. TrackMan also does not evaluate check swings.
The experiment with radar-tracking technology to call balls and strikes was originally expected to begin at the start of the season but experienced some delays.
White said at the All-Star break that he feels his organization is on the cutting edge of a movement.
"We're very excited about what this portends not only for our league but for the future of baseball," he said. "What we know is technology can help umpires be more accurate, and we're committed to that. We think the Atlantic League is being a pioneer for all of the sport."
The Atlantic League has an agreement with Major League Baseball to test rules changes.
Other rules changes being tested:
• Batters can try to steal first base on any pitch that was not caught in flight. It expands the traditional dropped-third-strike rule to all pitches, and batters can be thrown out if they try to run.
• One foul bunt is allowed with two strikes before it becomes a strikeout.
• Pitchers are required to step off the rubber to try a pickoff.
• There is a relaxation on check swings to be more batter-friendly.
The Associated Press contributed to this report.