Madrid are understood to be ready to pay £20 million to land the Holland international.

They have also drawn up a salary package, including image rights, which the Dutchman would accept, but Chelsea coach Jose Mourinho insists he wants the winger to remain at Stamford Bridge.

Schuster said: "It could be expensive. It is necessary to go slowly. We need to be prepared to make signings until the final day of the window.

"I would be much happier if they were here. The signing of Robben is very important for us."