Fitts left Monday's game against the Orioles with an apparent arm injury, Christopher Smith of MassLive.com reports. He allowed three runs on two hits and three walks while striking out six over four innings before exiting.
Fitts came back out for the sixth inning but was removed after tossing one pitch. He'll presumably be taken to the clubhouse to be evaluated further. Steven Matz was called upon to replace Fitts.