Ottavino walked around the mound somewhat dazed and pointed to the front of his left shoulder while chatting with first baseman Bobby Dalbec before manager Alex Cora and a trainer came jogging out. He walked off on his own and was replaced by Garrett Whitlock.
The team announced at the end of the inning that he had a "left shoulder contusion."
"He's OK," Cora said. "A little bit sore, nothing structural.''
Mateo's liner caromed off Ottavino and into right field for an RBI single, which ended up being the Orioles' last run of the game.
The Associated Press contributed to this report.