The left-back, who had just agreed to spend another two months on-loan at Bramall Lane, has returned to Fulham for treatment on a foot injury he sustained during the Blades 1-0 home defeat to Sunderland last weekend.
Blades boss Neil Warnock told the Sheffield Utd official website"We have sent Jon back to Fulham for them to take over his rehabilitation.
"We will know more about the damage to his foot in a week or so when the swelling goes down."