An intermediary for the deal claims Napoli are asking €4m for Miguel Britos, with Besiktas offering €2m.
The Uruguayan centre-back seems certain to leave the Partenopei this summer, having made just 17 Serie A starts last season.
“Britos could do well at Besiktas, the Turkish club consider him an interesting player,” go-between Kemal Can Tekin told Radio Crc.
“Napoli’s asking price is €4m, while Besiktas’ offer is €2m. Britos can be very useful to the Turkish side’s cause.
See the latest Serie A predictions and betting tips with Eurotips.co.uk