The North Queensland Cowboys confirmed on Monday that co-captain Matt Scott tore his anterior cruciate ligament in Friday's Round 2 game against the Broncos in Brisbane.
Scott left the field in the second half and scans over the weekend confirmed the injury. He will now undergo surgery on his knee.
"It's obviously a huge blow for Matt and he's understandably devastated," Cowboys coach Paul Green said.
"He'll have surgery then start his rehab, and knowing the type of player and person he is, he'll approach his recovery in the same dedicated way he trains and plays… with 100 per cent commitment."
The Cowboys had two other players injured in Friday night's golden point win, with winger Antonio Winterstein (broken arm) and fullback Lachlan Coote (torn calf) set to spend several weeks on the sidelines.
Green will tomorrow name his 21-man squad for Saturday's Round 3 match against the Manly Sea Eagles at 1300SMILES Stadium.