NEW YORK -- The injury-depleted New York Yankees have lost yet another key player.
Andy Pettitte, who left his start early Thursday night, has been placed on the 15-day disabled with a strained left trapezius muscle (upper shoulder/back).
"We don't think it's overly serious, but we want to play it safe," general manager Brian Cashman said.
Pettitte's next scheduled start was Tuesday in Baltimore.
Cashman said the team's recent string of games also factored into the decision. CC Sabathia had a start cut short by rain in Colorado last week, the Yankees played a doubleheader in Cleveland four days ago, and Phil Hughes lasted just 2/3 of an inning in his outing two days ago -- all of which put extra pressure on the bullpen.
"It could be overly cautious, but I also understand," Pettitte said. "I probably need a few days to let it calm down before I can throw a bullpen, and I need to pitch on Tuesday, and they don't want to send me out there in Baltimore on Tuesday and start warming up and it locked up and then we don't have pitching. We're on a tough stretch right now, so I understand."
The 40-year-old Pettitte is 4-3 with a 3.83 ERA. He doesn't anticipate having to sit out more than the mandatory 15 days.
"I feel good, I really do," Pettitte said. "It spasmed up so bad last night that I think I'm just sore from that. It is still sore, but I feel good."
Catcher Chris Stewart also left Thursday's game early with a left groin injury. Stewart had an MRI, which came back clean. But he is not in the lineup for Friday night's game against the Toronto Blue Jays.
"Walking's fine. It's just running. When I push off, it's still there a little bit," Stewart said. "So give it a couple of days, and then hopefully [I'll] be back out there."
The Yankees have only one other catcher on the active roster, Austin Romine, who will start Friday. Stewart will be in uniform and available to play in an emergency.
"If [Stewart] wasn't a player at all, that would be an issue. But he could catch if we needed him to," Girardi said, adding that infielder Alberto Gonzalez could play behind the plate if necessary.
Designated hitter Travis Hafner has missed the team's past four games due to a sore shoulder but was slated to take batting practice before Friday's game.
"He's gonna hit on the field today and try to turn it loose," Girardi said. "If he can turn it loose for me, then he is a player for us tonight."
Hafner will not start, since the Yankees are facing a left-hander (Mark Buehrle), but he could be available as a pinch hitter.