Sheffield United fear summer loan signing Keith Treacy could be ruled out for the rest of the season. The Blackburn winger, 21, who agreed a six-month loan deal at Bramall Lane in the summer, sustained the injury during Saturday's defeat at Swansea.
Blades boss Kevin Blackwell said: "It isn't looking too good and we'll have clarification after he has had a scan at 5pm.
"If it turns out to be cruciate ligament damage he will be out long-term, in the region of six to nine months.
"He knew something was wrong straight away when he felt his knee lock and then go backwards."