The Russian winger sustained “scalding burns” to his legs in an accident at home and is out week-to-week, the Blues announced on Monday.
Fellow forward Jimmy Snuggerud, meanwhile, is out at least six weeks with a left wrist injury that requires surgery, the team said.
Toropchenko, 26, has one goal and one assist in 17 games this season.
He found himself in the middle of a slight controversy on Saturday when he was ejected for a knee-on-knee hit against Utah Mammoth forward Logan Cooley.
Snuggerud, 21, has yet to miss a game this season, putting up five goals and six assists in 26 contests.
The Minneapolis native made his NHL debut with the Blues last season after being selected in the first round of the 2022 draft.
In a corresponding move, the Blues recalled forward Aleksanteri Kaskimaki from the AHL’s Springfield Thunderbirds. The 21-year-old, a third-round pick in 2022, has four goals and three assists in 16 games.
The Blues return to action Monday when they host the Anaheim Ducks.