LAS VEGAS -- Mark Prior missed a weekend in Las Vegas and appears headed for the disabled list on Opening Day to give him more time.

The Chicago Cubs trimmed the roster Saturday, announcing that outfielder David Kelton and pitcher Sergio Mitre were optioned to Triple-A Iowa.

Cubs manager Dusty Baker said outfielder Jason Dubois and pitchers Jon Leicester, Todd Wellemeyer and Michael Wuertz all made the big league team. The team will open the season with 12 pitchers.

The Cubs were not expected to make an announcement regarding Prior until Sunday.

"We'll save that for when we talk to him about it," Baker said after Saturday's final Cactus League game, a 3-2 win over the Seattle Mariners.

Prior threw 67 pitches over four innings against the San Diego Padres' Triple-A team on Saturday in Mesa, Ariz., at Fitch Park. He gave up seven hits, including two home runs, and walked three while striking out five. In three of the four innings, he was pulled early to keep his pitch count in check.

Prior has been slowed by inflammation in his right elbow. If the Cubs decide to place him on the disabled list at the start of the season, they could backdate that to March 25, and Prior could start April 12 which is the first time the team needs a fifth starter.

It's not that Prior isn't healthy. He just needs time to fine-tune some things.

Prior told reporters after Saturday's outing that his mechanics were "poor, for whatever reason, I'm not exactly sure why.

"As far as that's concerned, I'm not really worried about that," Prior said of his mechanics. "I can get those things ironed out."

He has been able to test his delivery on all his pitches. The right-hander has thrown only one Cactus League game, March 10, and been slowed because of inflammation in his right elbow.

"I threw some good pitches, and had a decent breaking ball at times," said Prior, who threw changeups and curveballs in Saturday's outing. "The most important thing is as far as my arm felt and my elbow, everything felt good."

Prior has been facing Cubs batters in simulated games as well as pitching coach Larry Rothschild, who has been willing to stand in at the plate.

"I know what I was doing," Prior said about his out-of-whack mechanics on Saturday. "I was getting under the ball, and getting under some pitches and got them up in the zone and ended up getting behind in the count, trying to come back. Obviously, these guys were ready for it."

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The good news is that Prior had no pain or discomfort Saturday.

"The elbow felt good, I threw all my pitches and let it loose for the most part," he said.

What's next?

"Right now, I'm just trying to get my arm strength, my inning strength -- or whatever you want to call it -- built up," he said. "I got close to 70 [pitches] today so you know it was a good thing. Hopefully I can make a start somewhere, wherever it is on [April 7], here or there, throw close to 80 pitches, and then make a determination from there."

Kerry Wood will have his final tune-up for the regular season on Sunday against the Angels' Triple-A team in Tempe. Rothschild said he wanted Wood to throw a minimum of two innings, with the session more for the right-hander to get into the routine of warming up. The right-hander is scheduled to start the home opener on Friday against Milwaukee.

Wood and Prior started more simulated games than Cactus League games. Does that mean Spring Training is overrated?

"No, it's not overrated," Baker said. "The length of Spring Training is basically for the pitchers. If they get off to a good start, they're still not going to be able to go seven or eight innings. That's what Spring Training is for, not only to get their timing and find the strike zone but get their endurance up."