Hunter lasted 4 1/3 innings in Sunday's start, allowing five runs on eight hits and a walk while striking out two. He surrendered a grand slam to Will Middlebrooks that allowed the Red Sox to pull even. The 25-year-old right-hander has allowed at least one home run in each of his past five starts.
"If we hadn't had yesterday, we probably wouldn't have done this," Orioles manager Buck Showalter said of the roster moves, which included catcher Ronny Paulino being optioned so the O's could select the contract of right-hander Stu Pomeranz and recall righty Jason Berken.
"I understand that Tommy had a slight oblique [injury] -- which he's 100 percent back from now -- he had the flu that everybody had and he had an ingrown toenail, so he went about two weeks without being able to do the strength stuff," Showalter said. "I'm hoping that he can take a breath and get back into the routine he was on when he was as strong as he's been his whole career, as he said, in Spring Training."
Hunter, who's 2-1 with a 5.00 ERA and has given up nine homers in 36 innings, said he understood the decision. The right-hander -- one of five former Rangers who received a 2011 American League championship ring before Monday's game -- will try to get back on track while with Norfolk.
"I've just got to pitch better," Hunter said. "They've got to make room for a couple of guys, and I'm the one who pitched last and gave it up in the fifth. It makes sense. Heck, it's a business. I've got to get better."
Hunter, who had been pushed back before Sunday's start, which he made on an extra two days' rest, reiterated that his struggles are not anything physical and that he simply needs to work on keeping the ball down.
Berken -- who last pitched for Norfolk on Saturday, when he worked two innings -- is a candidate to take Hunter's spot in the rotation on Friday against the Rays if he's not used in relief for Monday's game. Showalter said the Orioles are also making adjustments in the event they need to recall a starter from Norfolk, with Chris Tillman -- already on the 40-man roster -- a strong possibility.
Tillman, who last started on Sunday, is in line to start on Friday at Triple-A. Hunter must remain in the Minor Leagues for a minimum of 10 days unless he is needed due to an injury.
Pomeranz, the brother of Rockies pitcher Drew Pomeranz, has been a pleasant surprise for the Orioles, and he impressed Showalter in frequent outings during Spring Training despite not receiving an official invitation. Pomeranz started the season with Double-A Bowie before being promoted to Norfolk, where he has allowed two earned runs in 13 1/3 innings.
"I'm just trying to do everything I can to make an impression," said the 27-year-old Pomeranz, who pitched for the Orioles in minicamp this past winter and was first brought to the organization's attention by special assistant Brady Anderson before signing in early February.
"I don't know what the key is. I'm going right after hitters and trying to get outs. That's all I'm focusing on."
The decision to option Paulino, Baltimore's backup, instead of third catcher Luis Exposito -- who was recalled on Friday and started Monday's game behind the plate -- was made because the Orioles want to see what they have in Exposito. The club would also like Paulino to get more consistent time behind the plate.
"He's done some good things for us, and I just want to let him catch every day down there and try and get back to where he's comfortable, build up some of his leg strength and get some consistent at-bats," Showalter said of Paulino, who missed the first three weeks of camp with visa issues and made the team because of an injury to Taylor Teagarden. "Luis has been doing well there, and it gives us an opportunity to look at him. Obviously, Matt [Wieters] needed a day after 17 innings."
Paulino hit .300 in nine games with the Orioles, but he cooled off considerably after a 4-for-4 debut, recording five hits in his last 26 at-bats.
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.