"I was feeling some discomfort in my shoulder area, so I tried to rehab it a little bit and do some preventative work," Rosscup said Friday. "It wasn't going away, so I figured it was best to get it looked at.
"It's nothing serious. They saw some inflammation and a little bit of fluid, nothing too serious. I should be down for a week or so and then start cranking it up again."
Rosscup had appeared in four games, and he gave up one hit and walked two. He was relieved that there is no structural damage.
"I don't want to hurt the team by going out there and trying to pitch through pain," Rosscup said.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.