Everton have been closely linked with Croatia international Domagoj Vida recently.
Turkish-Football first reported interest in the Besiktas defender at the early stages of the World Cup.
The Black Eagles only signed Vida back in January and he does have another four-years remaining on his deal but they are open to a potential sale.
Reports in Turkey claimed that the Toffees have offered €10 million in addition to Davy Klaassen in a part-exchange deal for Vida.
A Spor are now claiming that Besiktas want Klaassen but want €15 million as the transfer fee.
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Per the source, the Istanbul based outfit value the powerful defender as being worth €20m.
Besiktas want to hold off making a final decision until after the World Cup.
The offer is attractive to the Super Lig outfit as they have made finding a replacement for attacking midfielder Anderson Talisca a priority.
Vida has been in impressive form for Croatia playing an important side in his country reaching the quarter-final.
The 29-year-old has started in every game except the final group game.
The Croatia national side will take on hosts Russia in the quarter-finals next on Friday.
