MESA, Ariz. — The Chicago Cubs' biggest question mark heading into the season is the bullpen, which was overhauled over the winter with the departures of Kerry Wood, Bob Howry and Michael Wuertz.

When camp opened last month, there were six supposed locks — Carlos Marmol, Kevin Gregg, Aaron Heilman, Neal Cotts, Chad Gaudin and Luis Vizcaino — leaving an opening for one more reliever.

But with three weeks to go in camp, could one or more relievers be pitching themselves out of a spot?

"Yes," manager Lou Piniella said Monday. "We're going to take the pitchers that are pitching best here. I think it's probably going to be harder to earn a spot, and easier to lose it."

Piniella was not naming names, but Vizcaino appears to be the one in most danger of losing a spot. The Cubs must pay him $3.5 million this year, and another $500,000 to decline his $4 million option for 2010.

Piniella said he doesn't take contracts into consideration when evaluating the players on the field, and only looks for the best possible staff.

The Cubs' chances of trading Vizcaino are slim because of the overpriced contract, though if they packaged him with a prospect, they could explore a deal with Oakland for shortstop Bobby Crosby, who makes $5.25 million and is being shopped after Orlando Cabrera signed.

Jeff Samardzija has the best chance of joining the bullpen, assuming Sean Marshall makes the staff as the fifth starter. Samardzija is also being looked at as a starter, but he threw three strong innings in relief on Monday.

Is it time for Samardzija to concede to Marshall and concentrate on winning a bullpen job?

"Nah, I'm not giving Marshall anything," Samardzija said with a laugh. "We'll trip him up before anything else. I love 'Marsh,' and he's a great guy on this team, a great part. There's nothing better than some good competition for some spots.

"All we can do is go tooth and nail at each other, and then when the last day of spring training is over, who knows? Then we'll shake hands and get ready for the real season."

Piniella likes the idea that Samardzija is not giving in.

"I've said all along that Marshall has the inside track at this thing," he said. "But let 'em compete. It's a great experience for him, No. 1, and it's making (Samardzija) use all his pitches. It's going to make him a better pitcher, regardless.

"If he doesn't make the rotation, he's making a case possibly in the bullpen. It's important for him to pitch well."

If Vizcaino pitches himself off the roster, Samardzija and left-hander Jason Waddell could be the ones earning the final two spots. Piniella said he's impressed with Waddell, a non-roster invitee who has kicked around in the Giants system the last six years.

"He comes in and throws strikes, and has got a good breaking ball," Piniella said. "Left-handers don't take good swings off him."