"It's day by day," Ramirez said after the Cubs' 6-5 win over Colorado. "I'm not playing tomorrow and we'll see how it is Monday."
Ramirez was 0 for 3 with two strikeouts. He also bobbled a hard grounder in the fourth, an error that contributed to a four-run inning for the Rockies.
Jake Fox replaced Ramirez in the field in the bottom of the fifth inning.
Ramirez, who is hitting .317 with nine home runs and 33 RBIs, dislocated the shoulder diving for a grounder against Milwaukee on May 8. He was placed on the 15-day disabled list the next day and was activated July 6.
He said the shoulder has been bothering him most of this season.
"It's been sore for a while. I was dealing with the pain, I was good enough to play, but today I couldn't," he said. "Every time I swing the bat I finish high with my left hand so it's pretty sore every time I swing."
Ramirez's shoulder is another in a series of injuries that have hit Chicago. Earlier Saturday the Cubs placed pitcher Carlos Zambrano on the 15-day DL with muscle spasms in his back.
"This has been a season for all seasons with the adversities we've had," Cubs manager Lou Piniella said. "What are you going to do. You have to keep playing and tough it out. That's what these guys have been doing, to their credit."