Red Star Belgrade have confirmed "many clubs" are interested in their young star Marko Grujic.
The Serbian midfielder is a target for Inter Milan, Chelsea and Manchester United.
Red Star football chief Blazo Raosavljević told Sportske Zurnal: "Many clubs want the player, there is also a courtship by Napoli.
"At the moment, however, we have not received any formal offer, but if arrived a €6 million bid I'd repeat that our intention is not to give up the player before 31st August 2016.
"There are clubs who are going to pay the asking price. It is difficult to assess his value now, someone could offer &euror;10 million..."