D-backs manager Chip Hale said before the game that Delgado's ankle had been wrapped and was receiving treatment and that he thought Delgado would be fine, but the club realized the sprain would take longer to heal upon further evaluation.
"His ankle is to the point -- there's no break or anything -- but it's a sprain that's going to take longer than five, six days to get better, so we're going to get another pitcher up here," Hale said. "Just a bad sprain and we just feel like it's going to be too long before he can pitch again."
Delgado, whose right foot was in a boot after the game, said he initially thought the injury was worse than a sprain since he hadn't rolled his ankle before Tuesday.
"I was just running and I think I just bent my ankle. I just felt the pain and went to the ground. That's how it happened," Delgado said. "I was scared in the moment that it would be broken."
Delgado, 25, is 4-3 with a 2.79 ERA in 41 games. He said his right ankle was still a little swollen after the game.
Reed, 26, is 2-2 with a 5.92 ERA in 25 games with Arizona this season. He allowed four runs in two-thirds of an inning against the Padres on June 20 before being sent down to Triple-A. Reed went 1-1 with a 1.74 ERA in 11 games with the Aces.
Andrew Erickson is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.