Miley seemed like a long shot coming into camp, and even in the final days, it was thought the D-backs were going to send him to Triple-A Reno.
"I was expecting the worst and hoping for the best," Miley said of his thought process before Wednesday's decision. "And the best happened."
An injury to reliever Takashi Saito opened up a spot, and with the D-backs not having a reliever capable of throwing multiple innings, they decided to keep Miley, who is a starter by trade, instead of a reliever like Mike Zagurski.
Miley was 4-2 with a 4.50 ERA in eight games (seven starts) for the D-backs in 2011.
"I'm excited and just happy to be a part of this on Opening Day," he said. "I'm still hungry from last year."