Fabbri missed all of last season after re-tearing the ACL in his left knee. He originally tore the ligament Feb. 4, 2017, causing him to miss a sizeable part of the 2016-17 season.
The 22-year-old put up 29 goals and 37 assists for 66 points in 123 games with St. Louis before knee injuries put him on the shelf. If healthy, Fabbri's return gives the Blues another offensive piece up front after they signed Tyler Bozak and Patrick Maroon and traded for Ryan O'Reilly.
The Blues on Thursday also announced forward Nikita Soshnikov will miss the start of camp with a concussion he suffered while training.