Kilgallon, the Blades 'Player of the Year' for 2009 is likely to miss the final three fixtures of the season against Burnley, Swansea City and Crystal Palace due to knee ligament damage.
The Centre-Half yesterday went for a scan on his knee after he picked up the injury during the Blades 1-0 win at Reading and didn't feature in Monday's 0-0 draw with Nottingham Forest.
Blades boss Kevin Blackwell said: "If our worst fears are realised it means we'll have to go into our last three games without one of our most consistent and influential players."