The Welshman has struggled to make an impact at Bramall Lane since arriving in a £3million deal from Manchester City two years ago.
Blades boss Danny Wilson said: "Ched wants to move on and wants a new challenge. We need him off our wage bill, so it may be a case of having to let him go at less than his market value.
"It would be a positive if it happens quickly but I cannot put a timescale on it. It all depends when potentially interested clubs want to make their move."