The injury surfaced on an 0-2 count to Curtis Granderson, whom right-hander Tyson Ross eventually came in to face, replacing Blevins.
"I stepped wrong and landed in a hole," Blevins said after the game. "It seized up real quick when I made that odd landing. I tried to stretch it out, but it's still a little stiff."
The A's won't know much more about Blevins' status until Thursday morning, when they'll also hear news on Travis Buck, a late scratch Wednesday due to a strained right oblique muscle. The outfielder first experienced pain while swinging in the batting cage less than an hour before first pitch.
"I've never had it before," Buck said. "It's a freak thing, really. I was just starting to feel good, so hopefully it won't feel as bad tomorrow as it does today."
However, Buck couldn't hide a rather worried expression on Wednesday night, when he told reporters he's in pain every time he coughs or laughs.
"It hurts pretty good," Buck said. "It's unbelievable when something like this happens. It's frustrating."