Mirotic, who had won the starting power forward position in advance of Thursday's season opener in Toronto, suffered a concussion and what the team called "maxillary fractures." The Bulls added "surgery is likely required."
A source who spoke to Mirotic after he was released from the hospital said the forward suffered two fractures and placed an early estimate for his absence at "a few weeks, at least." He possibly will have to wear a mask upon that return.
In their statement, the Bulls said they are "evaluating disciplinary action." But a source said the team is merely following protocol for all such incidents by communicating with the league office and that Portis will be suspended for multiple games.
That means the team will be down two more rotation players for the short-term on top of injuries to Zach LaVine, Kris Dunn, Cameron Payne and Quincy Pondexter. While rookie Lauri Markkanen likely will draw more minutes, coach Fred Hoiberg also could utilize small lineups featuring Justin Holiday and Denzel Valentine at wings and sliding Paul Zipser to power forward.
So much for the good vibes and fresh start that mostly had defined training camp.
According to several witnesses, tensions heightened between Portis and Mirotic during a competitive scrimmage. Several words were exchanged over trips up and down the court. Some shoving escalated matters and Mirotic once moved in Portis' direction. And then Portis landed the lone punch, which placed Mirotic on the ground for several minutes before his hospital trip.
Mirotic had bulked up to 260 pounds this season to improve both his post play and defense. That weight gain will be challenged by this type of injury, which typically renders a play unable to eat solid food initially.
In that sense, the injury will mirror Mirotic's February 2016 saga. That's when a botched appendectomy caused a hematoma that required a second, emergency surgery. Mirotic lost close to 20 pounds then.
Mirotic signed a two-year, $27 million deal that contains a team option for the second season just before the start of training camp. He all along had expressed his desire to return to the Bulls and skipped his Spanish national team commitment for the first time to prepare for this season.
"I'm excited for this season," Mirotic said after the Bulls' exhibition finale Friday. "I've put a lot of work in and think I will do great things."
Portis drew consistent raves for his tireless offseason work ethic and reported to camp in great shape. He drew the start in the first exhibition, in part to reward him for his offseason commitment, one source said.
But Mirotic and Markkaken add the long-distance shooting element that Hoiberg favors. Even before this incident, signs pointed to Portis possibly being the odd man out ultimately in the rotation.
The Bulls consistently had stressed the word "culture" throughout training camp in the wake of the Jimmy Butler trade. That culture centered on hard work and competitiveness. Both were on display during the scrimmage before the incident crossed the line.
How the Bulls react to and recover from the incident will be telling.
Fights happen in sports. They have happened here. Bears center Olin Kreutz once broke tackle Fred Miller's jaw in a fistfight at a shooting range in 2005. Michael Jordan once punched Will Perdue in the head and, more famously, Steve Kerr in the face, producing a black eye for Kerr.
Those 2005 Bears went to the playoffs and those Bulls teams won championships.
The Bulls are far from those goals. Their aims of competitiveness and respectability now must first involve picking up the broken pieces left over from this fight.