"It just kind of kept bothering me," said Pomeranz. "I know what it is, there's some soreness up there, we'll see how it is tomorrow and go from there."
Pomeranz totaled 82 pitches before his departure, leaving two men on base with one out for reliever Edward Mujica, who left the frame unscathed.
The left-handed Pomeranz, making his eighth start of the season, allowed one run on two hits and walked five, with two strikeouts.
Jane Lee is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.