Schalke chief Rouven Schröder insists no offers have arrived for Matthew Hoppe.
However, Schroder says the USA international could be sold this month. He has been linked with Everton and Arsenal in England.
The S04 sports director said: “We do not want to rule out the possibility that the transfer market might move again with Matthew Hoppe's situation.
"(But) we have not received a written offer from another club."
BILD says enquiries have been lodged with S04 from England, Russia and Itay.