Jim Thome, who got the start at first base for the Phillies, left Saturday's 5-2 win over the Chicago Cubs with lower back tightness.
He was replaced in the top of the fifth inning by Ty Wigginton, who extended his hitting streak to 13 games with a single in the seventh.
Thome is listed as day to day.
Manager Charlie Manuel said after the game that Thome hurt his back while sliding into second base on Shane Victorino's fielder's choice.
This was Thome's fourth start of the season. He was 0-for-1 in the game with one walk and is now 2-for-18 on the season.