Scans have confirmed that Toyota Cowboys outside back Brent Tate suffered a ruptured anterior cruciate ligament (ACL) and cartilage damage in Wednesday night's State of Origin match in Sydney.
Once the swelling in his knee subsides, Tate will undergo surgery.
This will occur some time in the next fortnight.
Cowboys co-captain Matt Scott underwent surgery on his fractured cheekbone in Sydney today.
He is expected to be sidelined for around six weeks.