With Lucio we had 5 central defenders. Caceres is a central defender.
So we've released Lucio for his own reasons, and will bring in another DC when the window opens. So we'll again have 5 central defenders.
As it's clear you don't understand co-ownership deals it's no surprise you don't see the benefit of them. Sorensen playing 5 games a season here really does not benefit him, and it won't if he returns.
Caceres is not CB in my books, he is too offensive to play at full defensive mode, at least in Italy and in the biggest part of his carrier has played in the wings.
As a compromise, in Spain, where it is asked from the defenders to participate in the attack, he can be tolerated in a CB role, but IMO, having seen him playing with us before he go there, he cannot be a regular CB option in Italy.
Useful to have as a sub overall though, but in the event of an injury of one of our starters, Lucio would have been the option.
Marone is young enough to permanetly convert into a CB, but that would be a waste of a very promising all arounder, possibly a new De Rossi (who is also waste in the NT as a CB imo, and it only happens because Italy does not provides decent CBs anymore)
So, we are now in a situation that we only have 3 CBs and 2 half measures, if one of the three is injured, suspended, both for a long period or in a decisive derby, we would have to make a defensive solidarity compromise, without a dedicated CB. With Lucio gone, we indeed need an equivalently good CB option.
Such thing is virtually beyond Marotta's reach, as he has failed for too many consecutive years to find one.
To avoid being forced to sign a Borriello/Bendtner CB, we sould have kept Sorensen as a back up,
competing in 3 fronts at a time, would give him plenty more chances, than just 3 caps, Pogbs and Padoin already got more than that...