"He's going to be treated and the trainer said it'll probably be two or three days until he plays," Cubs manager Lou Piniella said.
Lee left Sunday's game in St. Louis in the fifth inning with lower back stiffness, which he has been battling during the last several days. He homered in his first two at-bats Sunday.
Lee visited a doctor Monday afternoon.
Xavier Nady will play first base on Monday.
Bruce Levine covers baseball for ESPNChicago.com and ESPN 1000.