Downie, who will have surgery, was injured in the second period of Tuesday's 3-1 win over the Los Angeles Kings at Pepsi Center.
The 25-year-old had an assist and six penalty minutes in two games this season. He had 13 points (11 assists) in 20 games for Colorado last season after he was acquired from the Tampa Bay Lightning in February.
He signed a two-year contract with the Avalanche in June.
The Denver Post reported Chuck Kobasew would take Downie's place in the lineup. It also said forward Brad Malone would be called up from Lake Erie of the American Hockey League, where he had 14 points in 37 games this season.
The Avalanche also remain without forward Ryan O'Reilly, an unsigned restricted free agent.
Life's about opportunity and how you respond to that opportunity, and obviously he must have some swagger about him, some confidence about him, because he was solid. He made some good saves. He was 6-foot-3 on every shot, which is a good thing for a goalie. He played well. We got a win.
— Maple Leafs coach Mike Babcock on rookie goaltender Garret Sparks, who made 24 saves in his first NHL start, a 3-0 win vs. Oilers
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