It stat time again.
I'm not keen on Koulibaly because I think United need a rebuild, de Ligt is the one. Here's a comparison stat chart of FIFA Index. It's ordered on my derived stat called "Avg Defend", which is just the average of Marking, Slide tackle, Standing tackle, Strength, Jumping, Aggression, Reactions, Interceptions, Composure, Heading.
There are four basic kinds of players in the table. a) Top centre backs, b) United centre backs & tall players (background peach), c) prospects (background light green), and players United have been linked to.
Notice a few things.
1. WhoScored ratings aren't much use, but most top centre backs have ratings over 7. Doesn't tell us much.
2. Some defenders are very limited in most areas of their play. Especially Koulibaly!
3. Alderweireld has a highly rated defensive partner. Take him out of that partnership and he may no do so well.
4. de Ligt has 2 more years left on his Ajax contract. At 19, he's already better than any defender United have. 2 years of improvement and he could be the best in the world.
5. According to my "Avg Defend", Blind and Matic would probably make as good a centre back as Jones!
6. Some other players, apart from centre backs, got included. I could not be bothered to remove them.
7. Apart from top players, there are lots of other centre backs better than United's. Had I included all of them the list would be much longer. I tried to only include younger ones.