aren’t they both left footed. While Koulibaly would be a great signing it really is unusual to see 2 left footed cbs play together. It would be strange to see him and Laporte as a pair.
before anyone says it doesn’t matter think about any teams which have or currently play with 2 left footed cbs. It’s one of those weird things in football, 2 right footers is fine but not lefties.
The only recent example I can think of is deschamps playing Umtiti and Lenglet (I think) together. Apart from that there isn’t anyone who comes to mind