Paxton was hit by a line drive on his left arm and promptly left Tuesday's game against the Athletics, Greg Johns of MLB.com reports.
Paxton gave up a leadoff home run to Marcus Semien and was struck by the line drive on his throwing arm two batters later. The left-hander didn't wait to be examined by a trainer or try to stay in the game, walking off the field almost immediately. The severity of the injury is currently unknown. Felix Hernandez took the mound for the Mariners in relief.