One former manager, Carlo Ancelotti, once labelled Koulibaly one of the best defenders he had ever worked with. High praise from a man who has coached Paolo Maldini, Fabio Cannavaro, Sergio Ramos and Chelsea legend John Terry to name but a few.
In eight years at Napoli under Ancelotti and others, he has transformed himself from a little-known centre-back from Genk to one of the finest players in the world in his position. Little wonder English clubs, well aware of his suitability for the Premier League, have courted him for so long.