The defender played in Senegal's 2-1 victory over Poland at the World Cup in Russian Federation and made the revelation when speaking to journalists after the game.
'I'am disappointed that he leaves like this but we have now a big coach.
Brazilian central defender David Luiz had been snubbed by manager Antonio Conte and Gary Cahill's poor form meant that Chelsea had to utilize a young Dane called Andreas Christensen in the heart of the defence.
The Spaniard's future at Chelsea has been under the scanner with Juventus believed to be interested and even the Blues have been linked with a move for Bayern Munich's Robert Lewandowski. We know we can win something with him.More news: How President Putin missed, reacted to Russia's 3-1 win over Egypt
"They [Chelsea] can expect nice football because he is a very good coach", Koulibaly told Talksport about Sarri. I hope he can win something with Chelsea. He then tried convincing the club board to make a move for him last summer, but failed to do so once again before the player penned a new deal with Napoli.
Maurizio Sarri's contractual situation with Napoli is expected to be sorted out by the end of June, according to Sky in Italy.
The Italian's representatives are finalising the details of his proposed contract with Chelsea and it has been made clear to the club that Sarri wants them to pursue the Juventus star. At Chelsea I think it will be the same.' He added. At Napoli, we enjoyed so much the play and the supporters enjoyed so much too.
The coach is known to be a master tactician and would also work well within the structure of the club's transfer policy.