"I felt something in warmups kind of similar to what I felt in spring training,'' the left-hander said.
He will get an MRI Monday as a precaution, but Pomeranz said he expects to make his next start.
"He wasn't able to reproduce any symptoms later in the day,'' manager John Farrell said. "We'll see what transpires tomorrow. We don't think this is anything long term.''
The team announced the injury in the fifth inning. Pomeranz (3-3) was given the loss.
Pitching in chilly conditions with light drizzle falling most of the game, the left-hander finished his warm-up pitches and rotated his arm before manager John Farrell and a trainer jogged to the mound.
After a brief discussion, he walked to the dugout. He gave up two runs and three hits while walking three and striking out three.
Rookie Ben Taylor relieved Pomeranz.