This guy is a charging bull. I used him as CB in a 3ATB formation and he was impassable. Nothing bad can be said about this card, he is the best possible pure beast-defender in the game (I had prime Cannavaro, prime Nesta, prime Hierro, prime Rijkaard, Puyol, Ramos, etc). His physicality is on another level, he grabs and catches anything near him. No escape.
TO ME, the only but huge "con" he has is his nationality and the team he plays in (Napoli). No FUTChampions-ready green links a part from Carniball Mertens (I hate him this year) and this really forces you in the construction of the team. Serie A doesn't offer much a part from Ronaldo and some defenders (speaking in terms of "FUTChampions-ready"), thus you have to settle for some players in order to have Koulibaly on full-chem. And even If you manage to fit him, you'll surely be bound in other links since the players you used to fit him will not give you freedom of choice.
I tried every combination possible, but (considering my preferences) I didn't find a valid solution. That's why I'm using Van Dijk instead of him, and that's why the Dutch costs almost twice the price of Koulibaly despite being defensively worse.
And it's a real shame.
Hoping for Serie A TOTS to have Insigne.
Simply the best defender in the game
He just can't be hybridized