The White Sox hoped it wouldn't require a trip to the DL, but results from Monday's MRI plus lingering soreness during an exam on Tuesday have the team thinking more cautiously with Peavy, who had offseason shoulder surgery that caused him to miss the first 37 games.
Aside from the MRI, Peavy went through treatments on Monday until 30 minutes after the club's 3-1 win against the Mariners.
"I can tell you I feel a lot better, but I just saw the doctor and think we have to go on the conservative route," Peavy said. "Obviously, I wanted to push through it and do what we needed to do, but I think we're looking at the disabled list just because of the MRI results and how sore my exam was with the doctor. [It's] disappointing, no doubt. I was feeling good and beginning to climb with my arm."
Peavy went 2-1 with a 4.66 ERA in five starts after coming off the DL to start the season, but was injured in his last start at home on Sunday against the Tigers, going just four innings and allowing six earned runs.
Before talking with Peavy following his exam, White Sox manager Ozzie Guillen said the team was likely to play it safe rather than rush the right-hander back into action.
"We've got to see what's best for the ballclub," Guillen said. "That's his push leg. It's not a bad injury, but it's a very dangerous injury and we have to be careful about it."
A move to the DL would also mean the White Sox return to a five-man rotation after expanding to six when Peavy returned on May 11 against the Angels.