Chelsea and Manchester City are two examples of teams to have seen bids rejected and United also failed in their pursuit of the player in 2019.
Koulibaly’s long-term future remains unclear, which the defender admitted himself during an interview with Gazetta dello Sport last year.
“In football, you never know what happens. I never spoke to Napoli about leaving. If we have to find a solution, we will find it, but I have never talked about the transfer market,” he said.
“I also read in the newspapers about my future. But I only want to think about playing, I am 100 per cent [committed to] Napoli and it bothers me to be linked, every day, to this or that European club.
“We will see what the president (Aurelio De Laurentiis) will decide and if he proposes to extend my contract, that would allow me to end my career here.
At the moment, I still have a three-year contract and I am not thinking of anything else but Napoli.”