Mirotic suffered a concussion and broken facial bones when he was punched by Portis in a dust-up during practice on October 17.
He is expected to miss four to six more weeks.
The Bulls suspended Portis eight games for his role in the altercation.
Chicago's vice president of basketball operations John Paxson told reporters on Friday that the club is sensitive to Mirotic's plight.
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"I'm not going to get into any specifics about what discussions we have had with any agents and players," Paxson said. "What I do want to say is we're really sensitive to this entire issue and what Niko is going through physically and mentally. We're trying to be sensitive to him.
"We don't have all the answers today. But just like in anything, as an organization we have to do what's in our best interests. That's the bottom line. And so we will.
"We understand what he's going through. We have to be patient. It's not something that's going to be resolved overnight. We're going to continue to communicate with Niko and his representatives and find our way through this."
Mirotic inked a two-year, $27 million contract with the Bulls before this season.