Javonte Green will miss two to four weeks with a strained groin.
Green was inserted into the starting lineup after Patrick Williams' wrist injury and has started 18 of his 29 games this season, averaging 5.8 points and 4.2 rebounds per game while shooting 36.4% from 3.
When Green is on the court, the Bulls are 6 points per 100 possessions better compared to when he sits.
"Javonte has played really well for us and he's been great," Donovan said. "It is a tough loss. I think he's complemented that first unit really, really well.
"He's been such a big part of our team and has played so well, but we'll have to figure out different ways to try and make up his energy. I think in a lot of ways when you're playing as many games as you are, even the back-to-back against Indiana and Washington you need energy. He's one of those guys that provide it."