Matt Harrison was examined by team physician Keith Meister, and the diagnosis is lower back tightness on his left side.
Harrison pitched five scoreless innings against Colorado on Sunday night before leaving. He allowed five hits with two walks and three strikeouts.
Harrison has been one of the Rangers hottest pitchers of late. He went into the game on a five-game winning streak, going 5-0 with a 1.43 ERA over his last six starts.
The Rangers have been hit by a number of pitching injuries. Neftali Feliz, Alexi Ogando, Derek Holland and Koji Uehara are all on the disabled list.
-- Drew Davison