Extra bases

James Russell, slowed this spring because of a tired arm, will make his Cactus League debut on Wednesday in the Cubs' game against the Mariners. Russell has appeared in more than 70 games in relief in back-to-back seasons, and Renteria said he is very cognizant of a pitcher's usage. The Cubs do have another lefty, Wesley Wright, who could pick up some of the workload for Russell during the season.

Javier Baez is taking ground balls at second and third before batting practice, and Renteria will try to get the Cubs' top prospect at one of those positions in a Cactus League game soon but is looking for the right shortstop to match up with. Baez will open the season at Triple-A Iowa at shortstop.

"We're going to make sure when we do put him there we're really comfortable and confident he can handle that side of the diamond," Renteria said. "I think it's pretty close."

Darwin Barney started his second game at shortstop on Tuesday, and Renteria said that would be the most likely pairing with Baez because they want someone with experience.

Mike Olt, who has not started at third to protect a tender right shoulder, is "getting close" to playing there in a Cactus League game. Olt did make a perfect throw on a double play in Monday's game against the Giants, which impressed Renteria.

• Shortstop Starlin Castro, sidelined with a mild right hamstring strain since March 2, was able to do some light baseball activity on Tuesday. He is expected to get into games early next week.

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.