The defenseman was injured at 1:42 of the first period in Game 3 of the Western Conference Second Round at the St. Louis Blues on Saturday when he was checked hard behind his net by Blues forward Ivan Barbashev.
Girard was helped off the ice by a trainer before being transported to a hospital for further evaluation.
"Looking back on it, I mean, it's a heavy collusion. He just catches him in a bad spot," Avalanche coach Jared Bednar said. "But I thought it was legal check, to be honest with you. He kind of goes in on his head side, but he got a lot of body there. Girard] was turned the wrong way, and he went in awkward and it was a heavy check. Unfortunate, but to be honest, I think it was a legal check."
***[RELATED: [Complete Avalanche vs. Blues series coverage]*
Girard had 28 points (five goals, 23 assists) in 67 regular-season games and was third on the Avalanche in average ice time per game (21:39). He had three points (one goal, two assists) in seven postseason games.
Colorado won 5-2 and leads the best-of-7 series 2-1.