Stewart was injured in a fight with Minnesota's Kyle Brodziak during a 7-4 Avalanche win over the Wild Saturday.
"It's a big hole in our lineup, obviously," said center Matt Duchene. "Other guys are going to have to pick up that slack."
Stewart leads the Avalanche with 11 goals in 23 games this season. He also has 14 assists.
Colorado is home against the Atlanta Thrashers Tuesday.