Blais suffered the injury during the Blues’ 3-1 win against the Tampa Bay Lightning on Tuesday. According to NHL.com’s Lou Korac, the 23-year-old did not participate in Wednesday’s practice and was originally listed as day-to-day.
The team says he will be re-evaluated in 10 weeks.
Currently in his third season with St. Louis, Blais posted five goals and eight points in 20 games this season. The Montmagny, Que., native was a sixth-round pick with the Blues in 2014.