By Harvey Byrne

Chelsea have made a £38million bid for Napoli defender Kalidou Koulibaly, according to a report.

Koulibaly’s agent told the Sun that Everton, Chelsea and Juventus were all interested in the 25-year-old defender.

Sky Sports citing Sky Italy have now claimed on their transfer centre page that the Stamford Bridge club have made an improved £38million bid for the Napoli star.

Koulibaly would become the most expensive player in Everton’s history if the Toffees were to match Chelsea’s offer and he chose to join the Goodison Park club, surpassing the club’s £28million record signing Romelu Lukaku.

The centre-back has been at Napoli for two years since joining from Metz for £6.5million, and has now played 60 times in Serie A.

The defender played 33 times in the Italian top flight in the 2015-16 season as Napoli finished nine points behind Juventus in second.

Koulibaly’s contract expires in 2019 and Napoli offered him a new deal this summer, but the Senegal international rejected the offer of an extension.

Ronald Koeman has been active in his search for players since arriving at Goodison Park this summer, but has been unsuccessful in the hunt for the likes of Graziano Pelle and most recently Axel Witsel.

In other Everton transfer news, the Toffees and Chelsea are also set to battle it out for Sporting Lisbon midfielder William Carvalho.