The 29-year-old has regularly been linked with a move to the Premier League in recent windows, with Manchester United initially the front-runners for his signature but Man City overtaking them as favourites this summer.
However, Napoli's £72m asking price once again put potential suitors off, with Man City instead bringing in Ruben Dias from Benfica in a £64m deal.
Italian outlet Corriere dello Sport claims that Man City's decision to change target surprised Koulibaly himself, who was sure that a switch to the Etihad Stadium was in the offing.
Man City even accidentally 'confirmed' the signing of Koulibaly during their Dias announcement, suggesting that a move was very much on the cards at one stage.
The report also claims that Koulibaly was happy to stay at Napoli, though, and that he has opened talks with the club over a contract extension including a pay rise.