The team’s first-line center, who will be re-evaluated in five weeks, suffered the injury in the second period of the Blues’ 4-3 win against the Vancouver Canucks on Oct. 16.
Stastny had contributed five points (one goal, four assists) and recorded a plus-4 rating through the first five games after accounting for 46 points (16 goals, 30 assists) in 74 regular season games a year ago, his first season with the Blues after signing as a free agent.
The 29-year-old center has played in 66 or more games in seven of his previous nine seasons. He missed time with a shoulder injury early last season.
With Stastny out for at least the next few weeks, the Blues (5-2-0, 10 points) could elevate Jori Lehtera to take his place on the top line with Vladimir Tarasenko and Alexander Steen or go back to David Backes in that spot. Lehtera has six points (two goals, four assists) in seven games this season, while Backes has two assists in seven contests.