KISSIMMEE, Fla. -- Catcher Toby Hall received bad news Saturday morning when the MRI taken on his right shoulder revealed "an unstable shoulder and a torn labrum."

For now, Hall will rehab with the Astros' athletic training staff. No plans for surgery are forthcoming. Hall is expected to miss one month, minimum, which could put him out of the running for one of the two open jobs behind the plate.

"It will certainly be an uphill battle for [Hall], but at this point, all we should concentrate on is trying to get better," general manager Ed Wade said. "We'll see where we go from there. He'll work with the trainers. I met with [team physician] Dr. [David] Lintner this morning and we said he would certainly treat this non-surgically and see how [Hall] progresses.

"It takes him pretty deep into the middle of March and we'll continue to evaluate along the way. At this point there's no downside to trying to do everything we can to see if we can get it strong again."

Hall, a non-roster invitee, was one of four candidates up for consideration for two jobs behind the plate and he appeared to fit the description of an ideal backup catcher. The pool is now whittled down to three: Humberto Quintero, viewed as the favorite to start the season as the No. 1 catcher, J.R. Towles and Rule 5 draftee Lou Palmisano. Wade also mentioned Lou Santangelo, who figures to receive more playing time in Hall's absence.

Hall, who will begin his rehab program immediately, is not ready to give up on the season.

"They're going to stabilize it, keep it strong as they can and hopefully I can play through it," Hall said. "If everything stays strong and I have a good spring, hopefully I can go ahead with what I hoped to accomplish this spring."

Wade has no plans at this time to pursue a catcher from outside of the organization and sounded comfortable with the three remaining candidates. However, the GM anticipates possible options toward the end of Spring Training.

"I think with the guys we have in camp, we're capable with coming up with two solid catchers out of the group we still have here," Wade said. "If that changes, I think there will be opportunities toward the latter stages of Spring Training to add on if we have to.

"I think a ton of players could be out there toward the end, because a lot of these [still unsigned] free agents that are out there right now are going to end up on rosters, and other guys are going to be squeezed out. I think there's going to be a pretty significant pool of players toward the end."