MESA, Ariz. -- The Cubs have more openings in their bullpen than they originally thought.

Angel Guzman was to undergo an MRI on his right shoulder Friday and most likely will not be ready by Opening Day.

"It doesn't look good," Cubs manager Lou Piniella said of Guzman. "We've been a little concerned about this for four, five days and it hasn't gotten any better.

"It's a shame," Piniella said. "It seems like the kid is jinxed. What it does basically is open the door for somebody else."

"It's sad," Cubs pitcher Carlos Zambrano said. "The guy works hard. ... Hopefully, the MRI is negative and he can come back and help us in the bullpen."

Jeff Gray, whom the Cubs acquired from Oakland and is another right-hander projected as a candidate for the set-up job, has yet to throw off the mound because of a strained groin.

"Gray is starting to get on the doubtful list," Piniella said. "Not doubtful; let's call it the 'borderline' list."

Guzman, who appeared in a career-high 55 games last season, compiling a 2.95 ERA, has had troubles with his shoulder and elbow in the past.

"If he misses any more significant time, it'll be harder for him to get ready," Cubs general manager Jim Hendry said. "He has a history where the discomfort comes and goes."

Right now, the only relievers set for the Cubs' bullpen are closer Carlos Marmol, right-hander Esmailin Caridad and lefty John Grabow. Both Caridad and Grabow would be the primary setup pitchers.

With Guzman and Gray out, there are more opportunities for the young pitchers such as John Gaub, Thomas Diamond, Blake Parker, and James Russell. Another arm Piniella likes is Andrew Cashner, the Cubs' No. 1 Draft pick in 2008.

"Cashner's a nice looking young kid," Piniella said of the right-hander. "That's going to be up to the organization. First of all, let's see how he pitches here. Let's see what the organization has planned as far as starter, reliever. I think Jim will make that decision and rightfully so."

Gaub, acquired from the Indians in the Mark DeRosa trade, made his Cactus League debut on Friday. He gave up two hits, including Ryan Roberts' leadoff homer in the seventh, in 1 1/3 innings.

"This is my first Major League camp, and I've been in the pitching [group] with Ryan Dempster, Carlos Zambrano, Sean Marshall and [Tom] Gorzelanny, and those guys have been awesome," Gaub said. "It's been a joy. You hear horror stories from some guys who say the veterans don't treat them well. Everybody's been great."

Gaub had a 2.93 ERA in 26 games at Double-A Tennessee and a 1.72 ERA in 26 games at Triple-A Iowa last year. The lefty has quietly gone about his business.

"I introduced myself to Derrek Lee the other day and he knew who I was and that was awesome," Gaub said.

Right-hander Jeff Stevens, another young pitcher competing for a spot in the 'pen, knows what Gaub is going through.

"Last year, I didn't know a soul in the clubhouse," Stevens said. "[Gaub] doesn't know a lot of these people yet. Everyone is real nice and really open and meeting the young guys and helping them out."

The hardest part may not be filling a spot in the bullpen but filling DeRosa's spot. He was incredibly popular in Chicago.

"That was the first thing I heard when I found out I was traded for Mark DeRosa," Gaub said. "I'm never going to be able to replace a guy like that. He was a fan favorite and it's tough shoes to fill. That's not a role I'm looking to take anyways.

"I'll be happy if I'm helping the team and we're winning," he said.

Gaub may not know the veterans well enough to be invited for dinner, but he does know there's an opening on the 25-man roster.

"The way I look at it is everyone's got a chance," Gaub said. "I'm not expecting anything. I'm just going to take this spring seriously and give everything I've got and whatever happens, if they think I'm ready, I'll accept that. If they think I need more time, they know what's best for me. I'm just going to go with the flow and see what happens."

Jeff Samardzija, Carlos Silva, Gorzelanny and Marshall are vying for the two openings in the rotation. Whoever isn't a starter was expected to slide into the bullpen.

"That's why we'll be looking at these young kids, and the ones who pitch well have a chance to make the team," Piniella said. "Let these guys compete and let's leave here with the best [pitching] staff that we can."

The Cubs' scouts are in Florida and Arizona, checking other teams' pitching staffs.

"Jim's trying," Piniella said of possibly adding personnel. "If he can get something done, he will."