"I'd say there's a better than average chance he's going on the disabled list," Showalter said of Pomeranz, who is scheduled to have an MRI on Monday morning and won't travel with the team to Toronto. "That's frustrating because he's a good-looking young pitcher who's pitched well this year and could help us. Hopefully, it won't be too long."
Pomeranz, who was recalled on Friday, said he threw anywhere from eight to 10 pitches -- all fastballs -- before feeling a pop in his left rib area on a breaking ball as he was getting ready to enter in the top of the seventh. The 27-year-old said he wasn't sure what happened, and has never had a similar injury, but he just knew he was in pain and needed to stop throwing.
"Doing anything is pretty painful right now," said Pomeranz, who has been a feel-good story for the O's in advancing from Double-A to the Majors after not even being in big league Spring Training. "I'm pretty upset. Definitely disappointed."
Pomeranz allowed his first earned runs of the season on a two-run homer Friday night. He did not allow an earned run in 10 appearances between Double-A and Triple-A this season, tossing three scoreless innings in his Major League debut on May 7 against the Texas Rangers.
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.