Napoli president Aurelio de Laurentiis has lifted the lid on Chelsea's attempts to sign Kalidou Koulibaly last year.

De Laurentiis has revealed the Blues made a £47m (€55) bid for the 25-year-old, but they turned it down as they didn't have a replacement for Koulibaly.

"Chelsea had offered €55m, but I told Conte that I could not give him up without first having a worthy substitute," De Laurentiis told beIN Sports' TV channel.

"[I will not sell him] unless Sarri tells me: 'I have Tom, Dick and Harry who are reliable: you give up who you want'."

Koulibaly is under contract at Napoli until 2021 and will not come cheap if he leaves Serie A.