Brighton midfielder Andrew Crofts has been ruled out for at least six months after rupturing his cruciate ligament.
The 29-year-old limped off midway through Saturday's 1-0 Championship win over Birmingham, and scans have since revealed the extent of his injury.
He has played 24 times for the Seagulls this season, scoring six goals.
Manager Oscar Garcia said: "Crofty has been great and I'm very sorry for him. But we have a squad with strength in depth to deal with these situations."