Angel ace Jered Weaver came out of Monday's game after 12 pitches, injuring his lower back while throwing a first-inning strike to New York Yankees cleanup hitter Robinson Cano.
After delivering a 1-0 pitch, Weaver leaped off the mound in pain. Manager Mike Scioscia and a trainer ran out to Weaver, who tried to talk them into leaving him in the game.
But after tossing a warmup pitch to catcher Bobby Wilson, it was obvious Weaver was in too much pain to continue. Frustrated, he walked off the mound and into the clubhouse.
Right-hander Bobby Cassevah came in to take his place.
Weaver (6-1), who pitched a no-hitter earlier this season, began the game tied for second in the American League in wins while owning a 2.61 earned-run average. Opponents are hitting just .190 against him.