It was not immediately clear when he was hurt. The nine-time All-Star and nine-time Gold Glove winner was replaced by Matt Wieters in the sixth.
Cardinals manager Mike Shildt said he expects Molina to be available Tuesday, when St. Louis plays a doubleheader against Minnesota.
Molina was batting .276 after going 0-for-2 on Monday.
The Associated Press contributed to this report.