Nottingham Forest boss Billy Davies fears midfielder David Vaughan could be out for around three months with a knee injury.
Vaughan, who is on loan at the City Ground from Sunderland, joins Chris Cohen, Kelvin Wilson and Dexter Blackstock on the long-term injury list.
Davies said: "He has picked up a fractured patella, which unfortunately will keep him out for the best part of three months.
"It's on a similar scale to the losses of Chris Cohen, Kelvin Wilson and Dexter Blackstock. David is a very important player. It's a huge blow for the club, the fans and the player himself.
"But we're developing a squad for the future, that is our objective when we sign this type of player, and we hope he'll be able to come back before the end of the season."
Meanwhile, Davies also confirmed Jack Hobbs, Rafik Djebbour, Danny Fox and Kevin Gomis will be ineligible for Wednesday's FA Cup fourth-round replay at Preston as they were not registered with Forest ahead of the original tie.
The Forest manager admits he was impressed with Djebbour and Fox during their debuts in the 3-1 victory over Yeovil on Sunday.
Davies said: "As a striker it's important to get that first goal, which Rafik now has. It will do him the world of good, we know there is still work to do with his fitness, but he'll certainly be delighted.
"Danny is in a similar position. He hasn't played for a number of weeks but I thought he acquitted himself really well."