He was diagnosed with tightness in the back of his right shoulder, something that has bothered him since his start last week against the Twins. The injury isn't deemed to be serious, and the White Sox want to make sure it stays that way.
"I'm not going to go and pitch Gavin again unless he's 200 percent [healthy]," manager Ozzie Guillen said. "I'm not going to listen to him say, 'Oh, I feel OK.' Nah, I'm not taking that chance. If we take that chance, all of a sudden we regret it."
After a foul ball from Oakland leadoff hitter Rajai Davis, Floyd first received a visit from catcher Ramon Castro. Guillen and trainer Herm Schneider came to the mound soon after that, and Floyd walked off the field.
"It felt like it progressively got inflamed more and more," Floyd said. "It felt like it wasn't getting better. I felt it every pitch, and it's one of those things that you [hope] is nothing serious, which I don't think it is. It's one of those things you don't want to get too serious."
He was replaced by Tony Pena, who ended up throwing six scoreless innings. Guillen said that if Floyd missed any of his next two starts, Pena would likely take over his spot.
Doug Padilla covers the White Sox for ESPNChicago.com.