Napoli will never sell their players to a team in Serie A. They're hoping for teams like Barca, Real, PSG and Man City to offer them astronomical sums.
How many benfica games did you see? And how few were those Chelsea early stage games, because he has been insanely horrible consistently now. The team and coach plays a part to exposing him too (AVB is so clueless in organising defence, talk about opposte of "New Mourinho"...), but damn has he done more then enough to expose his inadequacies.
Every defender at Chelsea is playing badly anyway, even if only DL gets mentioned. He lacks concentration for sure (and with time it will only get better), but he already proved he can be a BEAST at Benfica, europe included. The guy certainly needs a better environment to settle his game now... just like Torres. And it'll be hard to do such thing at this Chelsea, unfortunatelly.