"I got a call from [Mobile manager Andy Green], and he just asked what I'm doing," Peralta said. "[He said] 'I need to talk to you.' I was kind of excited. I thought I was going to go to Triple-A.
"He just came to my room and gave me the big news, like, 'Hey, you don't need Triple-A. You're going to the big leagues.' I'm still in shock."
Peralta was playing well in Mobile, hitting .297 and had an on-base-plus-slugging mark of .839.
Peralta, who was a pitcher in the Cardinals organization before suffering a left shoulder injury, is in his second year as a member of the D-backs organization. Before the D-backs signed him and sent him to Class A Advanced Visalia in 2013, he was playing with the Amarillo Sox of the American Association -- an independent league.
"I got released in '09 with the Cardinals," Peralta said. "I had two surgeries on my shoulder. So I just decided to give up pitching and start swinging. It's much better swinging."
Manager Kirk Gibson moved Ender Inciarte, who had primarily played left, to center field, replacing Pollock. Inciarte has played five games in center field for the D-backs this season. In the Minor Leagues, he played 431 of his 610 games in center.
Gibson said Inciarte, Peralta and right fielder Gerardo Parra could all play center if needed, but he was hesitant to put Peralta in center field on his first day with the team.
"A.J.'s been in the [outfield] rotation virtually every day," Gibson said. "So when you take that way, obviously it's going to change things. We have to figure out what the best way to proceed is."
Adam Lichtenstein is an associate reporter for MLB.com.