The Phillies selected right-hander Michael Stutes' contract from Triple-A Lehigh Valley to take his spot on the roster.
Right-hander Ryan Madson will close for the foreseeable future.
"Yeah, I'm alarmed," Phillies general manager Ruben Amaro Jr. said. "Anytime a guy goes on the DL, it bothers me. Hopefully it isn't serious. He's sore. He was a little better yesterday and a little more sore today. Hopefully we'll have good news."
"He's a big strong guy and he'll be coming back strong," Madson said. "He'll be back."
Time will tell, but losing Contreras is a big blow to the Phillies' bullpen. He has thrown eight scoreless innings in eight appearances with five saves in five opportunities. The Phillies entered Spring Training expecting Contreras, Brad Lidge and J.C. Romero to be key pieces in the bullpen, but each of them is injured.
"It's thin," Amaro said of the bullpen.
The projected Opening Day bullpen was Lidge, Madson, Contreras, Romero, Antonio Bastardo, Danys Baez and Kyle Kendrick. The bullpen entering Monday's series opener in Arizona is Madson, Bastardo, Baez, Kendrick, Stutes, David Herndon and Mike Zagurski.
Contreras, who was unavailable to comment following Sunday's 3-0 victory, had pitched five times in seven days. He threw 81 pitches in that span, including 26 pitches Thursday, when he last pitched.
"He had been pitching quite a bit," Amaro said. "I think it was just the work that he's done. He didn't indicate it was one pitch, just over time, especially after his outing on Thursday."
Contreras is 39, but Amaro said he does not believe age played a factor in his injury.
"Tenderness can happen to anybody," he said. "It doesn't matter what age they are."
Madson also has pitched quite a bit recently. He was unavailable Thursday and Sunday because of what he called normal soreness. Madson said he could have pitched if it were September in the thick of a pennant race, but is trying to be smart in April so he is effective when it matters most.
"Normal soreness and fatigue," Madson said. "The day I took off [Thursday], the next day I felt 100 percent. I wasn't just running at 60 percent or 40 percent. It just jumps that quick. If you can just get one blow in between sets, in between reps ... you know you are going to go two out of three. That's fine. Two out of three, then two out of three, then two out of three. ... You can manage it that way. That's the way they want to do it, and so do I. That's what's cool, we totally agree about how we are being used."
That might seem especially prudent with Lidge and Contreras injured. It would be disastrous to lose Madson at this point.
"It's a long haul," Amaro said. "We want to be careful with them. We don't want to use him too much, but at the same time, we're trying to win baseball games. Charlie is going to have to continue to use these guys. Fortunately our starting pitching has done a good job, but we'd like to have our offense maybe stretch things out a little bit to maybe give us more space."
Madson said he thinks the bullpen can manage without Lidge, Contreras and Romero.
"What's awesome about it is we've had another guy step up into a role," he said, referring to Bastardo, who picked up the save Sunday. "That's what we're there for. To step up, just like he did today. If that's what we need, that's what will happen. That's the way it's always been in the bullpen."