Following another stellar season at the Reebok Stadium which earned him a series of call-ups to Fabio Capello’s England squad, Cahill has found himself the subject of interest from the likes of Arsenal, Manchester City and Tottenham Hotspur.
But Coyle insists he is yet to receive an offer for the 25-year-old and, while he is willing to let the player go at the right price, the Scot believes the clubs in question are acting selfishly by allowing the matter to drag on.
"There had been tentative enquiries, but there has certainly not been firm offers," Coyle told reporters.
"I have said to Gary that as soon as there are, then he will be the first to know. But I think a lot of the speculation is certainly unfair on him at this moment.
"We know they have the interest, but if somebody is going to back that up, then do it - put your bid in, or if you don't, leave the kid alone and let him get on with his football. I think that is only fair for everybody.
"If it is going to happen, then the sooner it does the better - if not, let the boy focus on his career, which to this point has been great and will get better.
"He is a young player, he is only going to improve and he is established in the England squad. He has been a revelation for me during my tenure here.
"But I think it is only fair that they either come and get him now or they let him concentrate on his football."
