Falter was removed from his start Tuesday against the Angels due to lower-back tightness.
Falter threw just 65 pitches across four innings before being pulled from the game, during which he gave up three runs on five hits and no walks while striking out five batters. The severity of his injury remains unknown, so there's no telling if he'll be able to make his next start -- tentatively scheduled to come against the Dodgers on Sunday.