McCullers (undisclosed) exited Tuesday's game against the Blue Jays in the fifth inning with an apparent injury, Barry Davis of Sportsnet reports.
McCullers was tossing a decent game at the time of his injury, having only given up two solo home runs to Jose Bautista and Edwin Encarnacion. He was replaced by recently promoted Joe Musgrove, who took the mound for the first time in the majors. McCullers will be considered day-to-day until more information comes out from the club after the game or sometime Wednesday.