"It felt better for a while," manager Bob Melvin said. "At times it hasn't felt great and the last week or so it hasn't gone away. We just want to make sure everything checks out."
Before Tuesday, Pomeranz was the last healthy member of Oakland's Opening Day rotation not named Scott Kazmir, who was traded to the Astros in July. The club has five pitchers on the 60-day DL: Jesse Hahn (forearm), Kendall Graveman (oblique), Jesse Chavez (rib fracture), Jarrod Parker (elbow) and A.J. Griffin (shoulder); and Sonny Gray was shut down Monday with a left hip issue.
Pomeranz split time between the rotation and bullpen, posting a 4.63 ERA in nine starts and excelling in a relief role with a 2.61 ERA in 44 appearances.
Melvin applauded the southpaw's efforts to pitch in both roles and said he's not sure which one Pomeranz will fulfill next season.
"It's not easy to do that, and he's performed both as a starter and a reliever at times really well," he said. "It's all about the consistency and pitching to his ability because he has a lot of ability. But it's difficult to go back and forth. I think, all in all, it's been a successful season for him. We feel like each and every year, he's going to try and get better, and we feel like there's even more in the tank than what we've seen this year."
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.