Fortuna Dusseldorf chief Thomas Rottgermann insists Benito Raman will not leave for anything less than an "indecent offer".
Raman told Rheinische Post: "The offer must be indecent.
"Of course, it is an incentive to bring in money for several new players. But players on paper can be different on the field.
"But with Raman, we know what we have about him. We do not think about selling him."