With the top-of-the-table Bulldogs already significantly down on stocks, Salmon limped from the field in Saturday's come-from-behind win over Canberra.
Scans on Sunday showed a fracture, meaning he will require surgery, with Bulldogs football boss Phil Gould suggesting he would face a 10-week return to play.
Salmon's injury comes with Josh Curran, Sitili Tupouniua and Jacob Preston all still serving suspensions.
Curran has another match to wait before returning from a shoulder charge, while fellow second-rowers Tupouniua and Preston have another three games to go.
Kurt Mann is the man most likely to fill Salmon's No.13 jersey against the Sydney Roosters on Friday night.
Salmon had scored the Bulldogs' second try after they went to halftime down 0-20 on Saturday, before reigniting his feud with Ricky Stuart.
The 26-year-old ran to the nearest camera after scoring, pointed to his chest and shouted "weak-gutted dog", after Stuart referred to his as one in 2022.
The Raiders coach, who copped a two-game ban for the comments three years ago, would not buy into the matter after the game.
"Honestly, how much do you really think I care about that?" he said.
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