Scans have confirmed Brisbane's Kotoni Staggs ruptured his ACL in their NRL loss to North Queensland and will require surgery.
The 21-year-old centre was tipped to make his NSW State of Origin debut, but his injury caps a horror season for the Broncos who landed their first wooden spoon.
Broncos Head of Performance Paul Devlin said the extent of the injury was confirmed by MRI scan on Friday.
"Kotoni will meet with the surgeon before having reconstructive surgery of his knee," Devlin said.
Richie Kennar also suffered a shoulder injury during the match but has been cleared of serious damage.