FORT LAUDERDALE, Fla. -- The Orioles' starting staff began to take a more defined shape Sunday, when manager Dave Trembley ruled out two arms and got another back in the mix.

Trembley said that veterans Brad Hennessey and John Parrish would not be healthy in time to compete for an Opening Day berth in the starting rotation, but right-hander Adam Eaton introduced another element to the conversation by throwing batting practice for the first time with Baltimore.

Hennessey, thought to be an early favorite for one of three vacant rotation slots, has been sidelined with a sore right elbow. And Parrish, who has starting experience, has been nursing an irritated left shoulder. Both pitchers have had cortisone shots, and Trembley indicated that neither has rebounded as well as expected.

"I'm not going to talk about them anymore because I couldn't tell you when they're going to pitch," Trembley said. "I already felt like they'd missed enough time that they weren't going to have an opportunity to break camp with us. There's no sense of urgency now to get them out there. They're too far behind. We can't get them caught up."

Eaton, however, is another story altogether. The veteran signed with the Orioles last Sunday after being released by the Phillies and had only thrown once since joining his new club. Sunday's session was the first time he'd faced hitters in more than a week, and Eaton said he can't wait to get some game action.

"They're talking about an intrasquad game Thursday, but I've thrown to my teammates plenty this spring," Eaton said. "I'd like to go out there and get somebody and not mind busting them up-and-in with a purpose pitch. It will be nice to get out there and actually compete instead of competing against your teammates.

"It's kind of a lose-lose situation for everybody where your comfort level isn't great."

Trembley took that thought process into considersation and said that Eaton will likely pitch in a split-squad game Friday. And he also said that veteran swingman Mark Hendrickson, who has been sidelined with tightness in his lower back, will be healthy enough to pitch by Thursday's intrasquad game.

Hendrickson also threw batting practice Sunday, and Trembley said the Orioles need him back to full strength.

"He had some life on his pitches and he said that's the best that he's felt," Trembley said. "We need to get him going, too. We need to get him on the mound and in a game. We need to get him stretched out, because if he is in the bullpen for us, he's a long guy. We need to get him some appearances and get his pitch count up."

Hendrickson said the injury isn't chronic, and he also said it may have happened by trying to get loose too quickly. The southpaw has made one game appearance, and that came against his former Marlins teammates. In any case, Hendrickson said that he's looking forward to getting back out there at full strength.

"I think it was just a combination of things and maybe the fact that we had more batting practice," Hendrickson said. "I pitched in a game, obviously, coming out of the 'pen for two innings. So I had adrenaline, plus maybe from playing against Florida, it was a little bit too much too soon and I had it kind of tighten up on me.

"We'll be cautious with the intention of getting ready by April. I've got to remember what I'm preparing for and make decisions accordingly. It's always hard, no matter how much experience you have."

Eaton, meanwhile, has had a strange Spring Training camp. He said that he fully expected to be released by Philadelphia, and he wasn't surprised at all when that eventually came to pass. Still, Eaton said that he felt like he's regressed a little bit since he left Phillies camp in Clearwater, Fla., and that he's excited to be able to amp it back up in game action.

"Today, I woke up and said, 'Sweet, I get to pitch ... but it's against my own team,'" Eaton said. "It's a little different, but you get a little extra adrenaline, extra zip on the ball in the bullpen. And it increases through Spring Training when you face the other teams. Obviously, Opening Day is a whole new set of rules."

As far as feeling at home, Eaton said he's not particularly concerned. He felt at home immediately upon joining his new teammates at Fort Lauderdale Stadium and doesn't expect that to change from an exhibition game.

"Once you put that uniform on the first day, you're a part of the team," Eaton said. "Everybody's been real accepting and very friendly. Getting to know some of the guys has been fun. In my first interview with you guys, Aubrey [Huff] gave me a hard time. ... You always feel a part of the team once you get going."