Yahoo has the details:
Mirotic was taken to the hospital Tuesday after their shoving altercation during practice ended with an alleged cheap shot from Portis to Mirotic’s face, league sources told The Vertical. Mirotic is undergoing tests, but is expected to be out for the foreseeable future, league sources said.
And there’s this from Woj:
Portis is 6-foot-10, 250 pounds; Mirotic is 6-foot-10, 220 pounds. Both are young players with a lot to prove heading into a season in which the team is determining whom to keep for the future. Portis may have just sealed his fate as someone not worthy of a roster spot.