Chicago Bulls forward Bobby Portis publicly apologised for punching team-mate Nikola Mirotic in a fight during practice on Tuesday.

Mirotic suffered two facial fractures in addition to a concussion in the fight – the 2015 NBA All-Rookie First Team selection expected to be sidelined for up to six weeks with the injury.

Portis was hit with an eight-game suspension by the NBA following the incident and the 22-year-old fronted the media on Saturday.

"I'm wrong for what I did," Portis told reporters. "I want to publicly apologise to Niko.

"I feel like I let my fans, the Bulls organisation and most importantly my team-mates down. This is not who Bobby Portis is."

Portis and Mirotic have not spoken since the clash.

A first-round pick in 2015, Portis said he has tried to contact his team-mate, but has received no response.

Portis, who played his college basketball at Arkansas, said the fight had nothing to do with Mirotic winning the starting job and that he was "just competing."

"I got suspended and it's my fault," Portis said. "I take it as a man. I'm just trying to repair my relationship with everybody."