Speaking at a press conference with Fabbri on Thursday, Armstrong said the team is looking at many options to replace the 21-year-old.
The future Hall-of-Famer is third in goals (765) and second in points (1,914) all-time. Last season with the Panthers he had 16 goals and 46 points in 82 games.
Fabbri has a torn ACL that will require surgery. The injury was discovered after the team’s pre-season game against the Washington Capitals on Sept. 22.
This is the second ACL tear Fabbri has suffered in 2017. Last season, he was shutdown on Feb. 4 and had surgery on the same knee that is injured now.
Fabbri was a first-round pick by the Blues in 2014. In two seasons with the team, he has 29 goals and 66 points in 123 games.