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3/17/2014 3:59 P.M. ET

Castro planning to be ready for Opening Day

MESA, Ariz. -- Cubs shortstop Starlin Castro, sidelined since March 2 with a strained right hamstring, is continuing to make progress and feels he has enough time to prepare for Opening Day.

"I'm getting there," Castro said Monday. "I'm running hard, like 80 percent. [I'm making] good progress, ground balls, hitting light in the cage, too. I think [Tuesday] I can run the bases. Maybe this week, I'll get some at-bats in the Minor League [camp]."

Castro, who missed two weeks last spring with a left hamstring strain, did look good in workouts before the injury, which happened in the Cubs' third Cactus League game.

"Starlin was looking real well, and looked good at the plate," Cubs manager Rick Renteria said. "I'm not too worried about Starlin. His demeanor is pretty positive, pretty upbeat. I think he's trying to get himself ready for the season."

How much time does Castro need? He said eight to 10 games would be enough. The Cubs have two weeks of camp remaining.

"I'm working hard and I'll be pretty good by Opening Day," said Castro, who does not have any more soreness in his leg.

Olt limited by shoulder fatigue, may play third Tuesday

MESA, Ariz. -- Mike Olt was scratched from Monday's Cubs' split-squad game in Phoenix because of fatigue in his right shoulder, which has nagged him all spring, but said this isn't a setback in any way.

"We're just looking to keep him healthy for the rest of the spring and available," Cubs manager Rick Renteria said.

Olt has been limited to first base and designated hitter because of tenderness in his right shoulder, which he said is normal. He has yet to play third in a Cactus League game.

"I think this fatigue should be OK for us to get him over there," Renteria said. "We know he can play third base. It's just a matter of getting him over there."

If Olt passes all the tests, he could start at third base Tuesday night when the Cubs face the Rangers in Surprise.

"I'm just trying to get ready to play third," Olt said. "I think I've been putting a little toll on [my shoulder]. My main goal is to get out and play third. It's definitely not a setback or anything like that. We just felt like,'Hey, if we want to get out there soon, we have to take it easy.'"

He has been doing a lot of work at third after batting practice, making throws to first.

"It's a good thing," he said of all the work. "It's definitely a lot stronger than it's been. I think this could be a good thing for me to take a little break."

Extra bases

Carlos Villanueva, projected as a swingman for the Cubs this season, will make his first Cactus League start on Wednesday when the Cubs play the Rockies.

Villanueva is not on the list of candidates for the fifth spot in the rotation.

"I think he could be used if needed to be," Renteria said. "We're still trying to see the rest of the guys we have. We're still going to let the spring play itself out."

Chris Rusin, James McDonald, and Tsuyoshi Wada are the pitchers the Cubs are considering for the one opening. Wada was roughed up by the Mets in Las Vegas on Saturday.

"It seems like he gets a little better and then takes a step back," Renteria said of the lefty. "He wants to compete, he wants to do well. He's very driven to do well. If he doesn't, he's disappointed. We hope he continues to go out there and keeps grinding and keeps trying to better himself and show us what he's got."

Wada has given up seven runs on 10 hits and five walks over 5 2/3 innings in three games. Renteria said the club is still finalizing the schedule and couldn't say whether Wada would get another start.

• Outfielder Casper Wells was sidelined with back spasms and listed as day to day. Outfielder Mitch Maier has a herniated disk and has yet to be cleared to play in a game. Both are non-roster invitees.

Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.