The defender is not considered non-transferable by the club due to the financial effects of the coronavirus on football.
The price set for the Senegalese is only around €50 million which is low for a player who earns €6 million a season.
That price has alerted Premier League sides such as Manchester United, Liverpool, and Manchester City. It has also led to Koulibaly wanting assurances about whether he should be searching for a move or preparing for a new season with Napoli.
As has been reported by the print edition of Corriere dello Sport, the club seems more occupied by trying to extend Lorenzo Insigne’s contract.
Koulibaly has been linked with Premier League sides for many of the previous transfer windows but at 30-years-old, he may need to make the move now or not at all.