However, Derby County Chairman Mel Morris has said the Championship side want to retain the services of the former English international.
“We have made it very clear to everyone, but most importantly to Frank himself that we want to retain him at the club for the long term,” he told SkySports.
“If Chelsea want to hire Frank then it is in their gift to make an offer in pursuit of that. In the meantime, we will continue to put our best foot forward to continue without plans for the coming season.
“We will work closely with Frank in that regard so that he knows how much he is wanted by everyone associated with the club.”