The Diamondbacks recalled Diaz from Triple-A Reno on Thursday, Jesse Friedman of GoPHNX.com reports.
Diaz had four starts for the Diamondbacks in July, and he notched a quality start in the first two. In the third game he surrendered seven earned runs across three innings, but he bounced back in his final outing July 28 by allowing just one hit in five scoreless frames before returning to Triple-A. The right-hander worked out of the bullpen in his last two outings with Reno and should serve as a long reliever while up with the big club.