Fabbri missed the entire 2017-18 season after re-injuring his surgically repaired left knee during training camp in September 2017. He had torn his left ACL on Feb. 4, 2017, and missed the final 30 games of the 2016-17 season.
St. Louis selected Fabbri in the first round (No. 21) of the 2014 NHL Draft. He has 66 points (29 goals, 37 assists) in 123 NHL games and 15 points (four goals, 11 assists) in 20 Stanley Cup Playoff games.
Fabbri was cleared Tuesday to participate in hockey-related activities in preparation for training camp in September.
"He's doing very well," general manager Doug Armstrong told the Blues website. "He is up in Toronto working very hard and time is going to tell on this one. It's very difficult, you feel for Robby. He was projecting to be such a good player and then these two injuries kept him out a year and a half. We want to make sure we're not putting him in a position to fail when he comes (to training camp). He'll come back in and be hoping for the best, but expecting a little bit of readjustment. But health-wise he's doing good."
