Gasol, who missed four games last week because of the same issue, had been on a minutes restriction of about 25 minutes per game since returning to the lineup in a win Monday over the Sacramento Kings.
"Pau's going to sit out tonight," Bulls coach Fred Hoiberg said before the game. "We just got word of that. We knew going into the back-to-back that this was a very likely possibility that he would miss one of the games. He's got a little bit of swelling in that knee. We just don't want to make it something where it will blow up and miss a significant portion of the rest of the season. So we'll be cautious with Pau tonight even though he hasn't played a ton of minutes -- he's still in that stage where it could continue to swell, and if you overwork, it could put him out for an extended period."
While the Bulls want to be very cautious with Gasol's knee to make sure it doesn't get worse, they have only 11 regular-season games left and are 1.5 games behind the Detroit Pistons for the eighth spot in the Eastern Conference playoff race.
"It's a minimal amount," Hoiberg said of Gasol's swelling. "But he's got some soreness in there. Again, this is something that we knew potentially could happen with the injury, with the IT band, the way it is and still being symptomatic in that knee. So ... we'll start Cris [Felicio] tonight in his place."
The Bulls already were playing without E'Twaun Moore (hamstring), Cameron Bairstow (back) and Joakim Noah (shoulder). Hoiberg also revealed before the game that point guard Derrick Rose was dealing with some back stiffness following Wednesday night's game against the Knicks.
"He's doing OK," Hoiberg said. "He was sore in his back. He got treatment during the game, he got treatment after the game. Got treatment again this morning. He just had some tightness in his back but he seems to be OK."
Rose led the Bulls with 30 points in Thursday night's loss. He has dealt with several different injuries this season but didn't seem too concerned about the latest setback.
"I had a little spasm in my back [Wednesday], but today it feels a lot different," Rose said before the game. "It was hard to breathe a little bit [Wednesday], but I got some good rest last night and I rarely feel it."