Eyre received a cortisone shot on Monday, and will not play catch until Thursday. He's had a bone spur in his elbow for a few years.
"Now, it's getting worse and it's sore," Eyre said Tuesday. "They put some cortisone in there to calm the inflammation and see if I can pitch without some pain for a while, which would be nice."
Eyre would prefer to be in the Cubs' bullpen on Opening Day but recognized there is no rush.
"If it's best for the team, if [Carmen] Pignatiello or [Les] Walrond, or whoever they put in my place, can start Opening Day and throw without pain, I'll go somewhere to pitch for a little bit until I can," Eyre said. "It's all speculation, but if it feels good after I play catch on Thursday, and the cortisone works, then I'll throw long toss on Friday, and maybe a bullpen Saturday or in a game Sunday."
However, Eyre will not be throwing in Las Vegas. He will stay in Arizona for extended Spring Training and get his work done there.
"I'm not going to Vegas, I guess, which is good, because I don't gamble," Eyre said.
There is nothing wrong with ligament or nerve in Eyre's elbow. The spur has been there for awhile, he said, and it's creating some discomfort.
Eyre appeared in a career-high and league-leading 86 games in 2006 with the San Francisco Giants, but says that the problem isn't due to overwork.
"I wouldn't change anything in my career," Eyre said. "I'm happy. I have no regrets about pitching so much or whatever. That's what I play the game for. If it hurts a little, so what? You grit your teeth a little and work your way through it. That's what I had to do last year. It just took me a whole half to figure it out."
The competition for the bullpen spot will be decided between Sean Marshall and Pignatiello, although Cubs manager Lou Piniella was leaning toward Marshall.
"If Marshall can handle the job, basically it's his," Piniella said. "Let's see what he does here in the next couple days."
Marshall was to pitch out of the 'pen on Tuesday against the Giants. Pignatiello, though, has not walked a batter or given up a run in eight innings over eight games. He's served up three hits in that span.
"Marshall pitched well last year and did a nice job for us and I'm appreciative of that," Piniella said. "We have to find out in short order if he can pitch out of the bullpen. I know Pignatiello has had a really nice spring. What he's done basically is open the door for himself here if need be. If Marshall doesn't respond or can't handle this situation, then Pignatiello is the guy we're going to take."
Walrond was being considered, but he was assigned to the Minor League camp on Tuesday.
"He's been starting in this organization, but he got a lot work out of the bullpen, and he's going to Triple-A to learn to relieve," Piniella said. "We like his stuff and like his breaking ball, so he's another kid on the horizon."
Meanwhile, Eyre bid farewell on Tuesday to his recreational vehicle, which he was living in this spring at a mobile trailer park. A friend drove it north.
"[Derrek Lee] walked in and said, 'Wow, this is nice,'" Eyre said. "[Michael] Wuertz said if we go far in the postseason, and win a World Series, I'll lead the parade in the RV."
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.