Rizzo was in the Cubs' lineup Sunday for the series finale against the Reds. He was pulled from Saturday's game in the eighth inning because of the back problems, which he said started "barking" in the fifth or sixth innings.
"He felt he'd be fine [Sunday] and came in and said he felt good," Cubs manager Rick Renteria said.
Olt is the Cubs' backup at first.
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.