KISSIMMEE, Fla. -- The 25-man Opening Day roster is quickly taking shape, but it's possible that the Astros will not officially anoint a setup man prior to the start of the regular season on March 31 in San Diego.

When Spring Training began, manager Cecil Cooper targeted Doug Brocail as the leading candidate for eight-inning duty. But Brocail's performance has been spotty at best, and Cooper wants to wait before he makes a definitive decision.

"As it stands right now, until somebody steps up and says, 'I want it,' we'll probably mix and just go with matchups," Cooper said. "I'd love to see someone say, 'I want it' and take it. It makes your job a lot easier.

"Hopefully, someone will take it. There's still time. We'll keep running them out there. For me, the guy ideally would be Doug Brocail. That's kind of why we brought him here. But he scuffled this spring, and [Wednesday] night was really his first real good outing."

Brocail threw a scoreless ninth against the Braves in his most recent outing, but before that, he struggled. Brocail pitched one scoreless inning in his first outing of the spring, and he allowed at least one run in each of his next five appearances.

The veteran righty historically has never been that good during Spring Training, so Cooper isn't worried about Brocail in terms of the regular season. Still, Brocail's struggles apparently are worrisome enough to prevent the skipper from handing him eighth-inning duties.

"We'll play it by ear and see," Cooper said. "We'll definitely have to have something close to being in place. These guys need to know what their roles are and prepare for that."