Collmenter started the season in the rotation but was demoted to the bullpen after four rocky starts. He returned to the rotation to make five starts and has posted a 3-1 record and a 2.41 ERA in his past 18 appearances. Collmenter is 3-3 overall with a 4.24 ERA in 22 games.
The Diamondbacks recalled right-hander Brad Bergesen from Triple-A Reno. Bergesen posted a 1.80 ERA in five innings across three relief appearances in his previous stint with Arizona this season.
Bergesen had been claimed by the Diamondbacks on July 20 from Baltimore.