The 19-year-old Girard made his Stanley Cup playoff debut during Game 1 in Nashville, only to sit out the second contest with the injury. The Avalanche trail the first-round series 2-0 heading into Monday night's game at the Pepsi Center.
Girard was acquired from Nashville in early November as part of a three-team trade that sent Matt Duchene to Ottawa. Girard had three goals and 17 assists for Colorado in the regular season.
Coach Jared Bednar said Girard is a "big loss for us. We have to move on. The other guys are going to have to pick up the slack."