The Red Sox will place Fitts (biceps) on the 15-day injured list prior to Tuesday's game in Baltimore, Chris Cotillo of MassLive.com reports.
While Fitts seemed to avoid a serious injury when he exited Monday's appearance with right biceps tightness, the issue is bad enough to require him to miss at least a couple weeks of action. It's unclear who will slot into the rotation in Fitts' place, but Kyle Harrison, Payton Tolle and Walker Buehler are among the options.