Klassen is slated to start Saturday's game against the Reds in Cincinnati.
Summoned from Triple-A Salt Lake last weekend to make his MLB debut, Klassen faltered in his first start with the Angels, failing to escape the third inning while yielding two earned runs on three hits and five walks. Though the 24-year-old righty's control left much to be desired, he displayed lively stuff, recording four punchouts while finishing with a strong 30.1 percent called-strike-plus-whiff rate. With Ryan Johnson (illness) recently joining Grayson Rodriguez (shoulder) and Alek Manoah (finger) on the injured list, Klassen will get at least one more chance to prove that he's worthy of a spot in the big-league rotation.