Although Wagner, 26, was not pitching well for Triple-A Syracuse, acting general manager Mike Rizzo said there were no plans to take him off the roster.
"I don't really know what happened. It took us by surprise," Rizzo said. "He wasn't going to get replaced. He was still in the bullpen rotation."
Wagner said he retired because he has an injured right shoulder. He didn't want to have surgery and then rehab the shoulder for the next 18 months. Instead, Wagner will work with his father on their 35-acre farm and spend more time with his wife and children in Texas.
"I'm ecstatic to be home and spend my summers with my family," Wagner said. "My arm hasn't felt good for the last three weeks. I could have gone on the disabled list. I just didn't want to collect a pay check."
Wagner, acquired from the Reds in the eight-player trade in 2006, did not play in the Major Leagues last year because he was still recovering from right shoulder problems, but he came into camp 100 percent healthy this spring. Manager Manny Acta was impressed at how Wagner had life on his fastball.
"He worked so hard to come back from that surgery and he had his velocity back," Acta said.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.