Chiellini - Bonucci partnership seems very promising. So now we'd need one older defender to be a rotation and 3rd choice. IMO Marquez would be perfect while he can also balance midfield if needed.
He's for free so we could splash even more on a left back, which would be the key of creating one well composed defense.
True. But Campbell did very well against inferior opposition. While he looked out of place against the better teams, he was a complete rock against teams ala Stoke, Hull City etc, ie teams with strikers that used brute force rather than skill or agility. The same strikers we usually struggle against. In a way, with our circumstances and our personnel, it was a good strategic move.