Foster (5-0) struck out two and retired all six batters faced to earn the win Saturday against the Reds.
Foster came on for starter Dallas Keuchel, who lasted just four innings in his return from a back injury. It was the eighth time in 19 appearances Foster has thrown more than an inning, including two outings as an opener. Foster has been one of several gems out of Chicago's bullpen and sports a 1.88 ERA with 28 strikeouts over 24 innings.