Derby midfielder Paul Green faces a lengthy spell out of action with a serious knee injury.
The Republic of Ireland international suffered the problem during last weekend's defeat at Cardiff.
Scans have revealed Green has damaged cruciate and medial ligaments in his right knee and will undergo surgery in a month before embarking upon a lengthy rehabilitation process.
The injury is likely to sideline the former Doncaster star for up to nine months and his absence is a major blow for the Rams as they look to secure their Championship survival.
It means Green is also likely to miss the remainder of Republic of Ireland's Euro 2012 qualifying campaign.
Meanwhile, Derby have received better news on left-back Gareth Roberts, who was also stretchered off at the weekend.
His knee injury is not as bad as first feared and will only rule him out for the next two matches.