The hard-throwing Detroit reliever went back on the 15-day disabled list Wednesday with soreness in the right shoulder that was surgically repaired during the offseason.
Zumaya said his doctors believe the pain is not from a new injury, but from the tearing of scar tissue.
"I've been trying to be a hero and come back too fast," he said. "I've given it all I've got this year, even when people doubted that I'd ever pick up a ball again."
Zumaya injured his shoulder while helping his family pack to flee wildfires in California, and didn't join the Tigers until June 20.
Zumaya has gone 0-2 with a 3.47 ERA in 21 appearances, but has struggled badly with his control. He has walked 22 in 23 1-3 innings.
The right-hander took the loss Tuesday night against Toronto, walking three without getting an out.
"It's not working," he said. "I'm not going to pick up a ball for 12 days, and I'm not going to go out there and pitch until my arm feels 100 percent. Right now, I'm just bringing the team down."
Tigers manager Jim Leyland was encouraged by the diagnosis that Zumaya did not have a new injury.
"I think it is great news," he said. "He blew up scar tissue, and that's a process that he is going to have to go through."
The team purchased the contract of right-hander Francis Beltran from Triple-A Toledo to fill Zumaya's roster spot. Beltran is 2-5 with a 4.81 ERA in 36 outings with Toledo.
The Tigers did get some good health news from their bullpen, as Todd Jones threw off the mound without pain. He hopes to come off the disabled list Friday after being out since July 31 with shoulder inflammation.
"I threw about 20-25 pitches and faced a few hitters," he said. "I had good movement and good extension, which is nice, because I picked a bad time to get hurt."
The Tigers have one other injury to deal with, as third baseman Carlos Guillen expects to miss a few days with a pinched nerve in his back.
"I'm feeling a lot of fatigue in my legs and back," said Guillen, who had an MRI exam Tuesday night. "I'm going to rest it for 2-3 days and see what happens."