The Diamondbacks recalled Bratt from Triple-A Reno on Wednesday.
Bratt is set to make his major-league debut Wednesday in St. Louis with a start against the Cardinals. The left-hander was added to the 40-man roster over the offseason and earned his first big-league promotion after posting a 2.84 ERA, 0.95 WHIP and 42:12 K:BB over 44.1 innings covering 11 starts this season with Reno. Bratt recently returned from injury and threw only 48 pitches over four frames in his most recent start, so it's unlikely he'll be ready for a full allotment of pitches Wednesday.