In theory Skriniar should slot in the back-3 middle. But in reality I am quite skeptical, coz positioning isn't his strongest point. Several times when balls were lobbed behind his back he missed the clearance header and cost the goal.
Skriniar only shined as CB with his back covered by another in a back-4. As RCB in back-3 he was okayish, but that exposes his other weakness of speed when facing top wingers.
It could work, still, if he is instructed roaming forward to use his brutal press, more or less like a DM. But that negates how Inzaghi operates his side CBs.
Plus transfer fee + especially salary, I would s suggest skipping and find more suitable player.