Andy Pettitte left Thursday night's start against the Seattle Mariners in the fifth inning because of tightness in his left trapezius muscle, which is located in the upper shoulder/back area.
Afterward, Pettitte said his trap muscle wasn't tight anymore and he wasn't hurting.
He isn't sure if he'll have to miss his next scheduled start, on May 21 at Baltimore. The team doctor told Pettitte he believes it was just a spasm.
"I'm realistic, I know how these guys are. I asked them if I could stay out there and try to get through it," Pettitte said. "I'm hoping it's a spasm and it settles down. I know my back didn't loosen up [on the mound]. I can't tell you I've had this before; I haven't. But I don't feel it tight right now. I feel like it's loosened up and relaxed. I would think that's a good sign."
Via Matt Ehalt/ESPN