Chelsea wants Napoli's Kalidou Koulibaly - for £38 million

Chelsea has made a bid of £38 million ($50 million) for Napoli's Kalidou Koulibaly - which would be their biggest signing of the transfer window yet, according to Sky Sports.

Manager Antonio Conte wants the 25-year-old to strengthen Chelsea's defence. The club has already signed Michy Batshuayi and N'Golo Kante for £33 million and £30 million respectively.

Koulibaly's agent Bruno Satin said his client refused to sign a new deal with Napoli, Sky reported, and that Chelsea was very interested.

Gonzalo Higuain, who also played for Napoli, signed to Juventus this week for £75.3 million ($99 million) - the third-highest transfer fee in history.

Koulibaly's contract at Napoli lasts until 2019, but with the club knowing he wants to leave and Chelsea offering so much money it seems likely Napoli will agree a deal. It would be a coup for the Chelsea, as Koulibaly is considered one of the most versatile defenders in the world.

Either way, Chelsea does not have long to get Koulibaly if it wants him to start at the beginning of the season - the club's first game of the new Premier League season is against West Ham on August 15.

NOW WATCH: 50 Cent will pay $23.4 million to creditors over the next 5 years - here's how he made and lost millions

Please enable Javascript to watch this video