Marcus Stroman lasted just three innings on Wednesday night, his shortest outing in three years, because of tightness in his right armpit.
"It's not something I'm slightly concerned with," Stroman said. "Just general tightness in my armpit. Just caution on the side of being safe."
Stroman allowed five runs on six hits against the New York Yankees.
"Got to be smart, get him out of there," John Gibbons said. "Plus, tough night for him, anyway. He wasn't going to last much longer, anyway."