Sanchez will return to Detroit and undergo an MRI on Saturday to determine the severity of the injury.
Sanchez lifted his right arm as if trying to stretch after striking out Josh Thole for the second out of the fifth. Detroit's trainer went to the mound and could be seen massaging Sanchez's pectoral muscle, next to his armpit. After trying a warm-up pitch, Sanchez walked to the dugout and was replaced by left-hander Blaine Hardy.
Sanchez allowed four runs and 10 hits in 4 2/3 innings. He walked one and struck out three.
Information from The Associated Press was used in this report.