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Harley was left frustrated at the weekend after the clash with Reading was postponed.
And having already missed out on the Worthington Cup round 3 victory over Leeds United, the former England Under-21 international has not played as many games as he would have liked.
The Blades will be forced to take a decision over whether to extend his spell in South Yorkshire, and assistant boss Kevin Blackwell told the Sheffield Star: "Jon's only got a week left now.
"It goes without saying that what happened on Saturday was a big shame not only for us but for him personally."
Harley arrived as cover for Robert Ullathorne and could be kept on as the defender is still some way off a first-team return.