Stewart was called up for his start against the Padres during Game 1 of Saturday's doubleheader.
Stewart will make his fourth spot start of the season for Los Angeles, his latest coming against the Pirates on Aug. 22. During that game, the right-hander allowed five earned runs in just two innings. Over the course of the season, he's made 10 major-league appearances, posting a 3.38 ERA and 1.29 WHIP and a 17:11 K:BB.