Emotions were running high at Wrigley Field on Thursday when home plate umpire Andy Fletcher lost his cool, charging the mound to exchange words with Jon Lester.
Chicago manager Joe Maddon eventually intervened and took over the confrontation, protecting his players from getting into it with an official.
It's unclear what incited the incident, but according to the Chicago Tribune's Mark Gonzales, Lester claimed to not have said anything directly to Fletcher.
"I don't know why (Fletcher) was so upset," he said. "I had my head down when I was yelling. He went AWOL. I don't know what was going on. It has nothing to do with umpire's strike zone."