EurosportGallinari hobbled out of the arena on crutches and wearing a walking boot after injuring the foot in the third quarter of Monday's 99-90 loss to the Houston Rockets.
X-rays revealed a chip fracture in the foot and additional tests will be performed Tuesday.
"I'm not happy it happened to me," Gallinari told the team's website (www.nba.com/nuggets). "I wanted to play (after the injury) and I wanted to win this game more than anything. I'll be out I don't know how long."
Gallinari, a forward who recently signed a four-year, $42 million contract, was averaging 17.0 points and 5.2 rebounds while starting all 25 games.
The Nuggets already were playing without three starters - power forward Nene (strained heel), center Timofey Mozgov (sprained ankle) and shooting guard Arron Afflalo (sprained ankle).
The injuries come with Denver sitting in second place in the Northwest Division, four and a half games behind the Oklahoma City Thunder.
"No one is going to feel sorry for us except ourselves, and if we feel too sorry for ourselves, we're not going to bounce back," Nuggets coach George Karl said after Denver's third consecutive loss.
