Delgado injured his ankle during a conditioning session before Tuesday night's game in Seattle. He is 4-3 with a save and 2.79 ERA in 41 relief appearances with the Diamondbacks this season.
Reed was 2-2 with three saves and a 5.92 ERA in 25 games before being optioned to Reno on June 22. He went 1-1 with five saves and a 1.74 ERA in 11 games with the Aces.
Reed had 32 saves in 2014 after arriving in a trade from the Chicago White Sox and opened this season as Arizona's closer before losing the job in May.