Chicago Bulls starting power forward Nikola Mirotic sustained what the team called "maxillary fractures" after being punched in the face by teammate Bobby Portis in a practice altercation.
According to the Bulls, Mirotic likely will require surgery.
The Chicago Tribune reported the injury would keep Mirotic out for a minimum of a few weeks.
ESPN reported that Mirotic charged at Portis twice before Portis threw a punch and connected with Mirotic's face. Mirotic dropped to the floor and lay there for several minutes before getting up. He was taken to the hospital and released later Tuesday.
The Bulls are evaluating disciplinary action, and ESPN reported Portis would be suspended for multiple games.
Just before the start of training camp, Mirotic, 26, signed a two-year, $27 million deal that contains a team option for the second season. He has averaged 10.8 points, 5.3 rebounds and 1.2 assists over his 218-game NBA career.
Portis, 22, a 2015 first-round pick by the Bulls, averaged 6.9 points and five rebounds over 126 games the past two seasons.