The team will have a better timeline for his return once he's evaluated back in Denver.
The four-time All-Star left in the third quarter and did not return. The Nuggets saw their seven-game winning streak end in a 113-107 loss.
Millsap scored 16 points to go along with 3 rebounds and an assist in 19 minutes before suffering the injury Friday.
In his 13th season, the 6-foot-8, 246-pound Millsap is averaging 13.5 points and 7.1 rebounds per game.
Information from The Associated Press was used in this report.