Derby County captain Shaun Barker will miss at least the rest of this season after dislocating his right kneecap in the 1-0 win over Nottingham Forest.
Barker was hurt making a clearance and needed six minutes of treatment before being taken off on a stretcher.
The defender was then taken to hospital and will have a scan on Wednesday.
Manager Nigel Clough said: "We are gutted for Shaun. It has taken the gloss off the win somewhat because he is such an influential figure."