Twitter users directed Donovan's tweets to the attention of reporters during a doubleheader in Chicago, including at least one that used an anti-gay slur. Donovan's Twitter account was deleted shortly after the second game, in which Donovan hit a two-run double in the 10th inning to spur a 7-4 Cardinals victory.
The flagged tweets were sent in 2011 and 2013, and the 25-year-old Donovan said Saturday they were part of "playful banter" with a friend.
"I take full responsibility," Donovan said. "It was something I sent out a long time ago. I'm truly sorry to anyone I may have offended. Anyone that knows me as a person knows I see everyone the same, and I do not condone that type of behavior or anything.
"If I've offended you, I truly apologize. Hopefully, I can do my part to show you that's not who I am."