The veteran forward did not participate in Monday morning's shootaround and was re-evaluated once he got to the United Center prior to tip-off.
"[He] didn't shoot around this morning," Bulls coach Vinny Del Negro said before the game. "He's got some swelling in that knee. And with the back-to-backs he's a little bit sore, so he'll try to warm up and see how it feels."
James Johnson started in Deng's place. He scored nine points in Chicago's 116-92 loss.
Joakim Noah (plantar fasciitis) also sat out Monday night and Del Negro hinted that it could be a while before Noah sees the court again.
On the bright side for the Bulls, Derrick Rose (sore knee) played.
"It's hard," Rose said of all of the injuries. "With the players that we have, they're trying to play through it. The people that we just got, they're good players. So, we're not worried about who's out or whatever. We know we're missing some players, but we can't use that as an excuse."
Nick Friedell covers the Bulls for ESPNChicago.com.