Chelsea have brought in four new first-team players this summer.
"I really like the Matic signing", he said in an exclusive BT Sport Facebook Live ahead of Tuesday's UEFA Super Cup.
"But I repeat - for sure this a gross loss, a great loss for us".
"I can't think of a reason why Chelsea would sell him", Neville told Sky.
He has however warned that Chelsea must build on that success. I have scored 15 or 16 goals and won titles.
Mee was the lesser heralded, certainly outside town, of his centre back pairing with Michael Keane last season, but after Keane's departure, he will be the main man: "We were a duo but I felt the responsibility past year as well, I was the more senior player of us two".
"It's the price you have to pay for such a big transfer". And it's something that motivates me and makes me work harder every day, to spend an hour every day in the Sports City training.
And while Chelsea have moved to plug the gap by signing Tiemoue Bakayoko from Monaco, Scholes is not convinced Blues boss Antonio Conte has got the better end of the deal. "But you know very well that there are surprises".
Things are more comfortable on the personal front for Conte, who recently signed a new, improved contract and will have his family - wife Elisabetta and daughter Vittoria - living with him in London this season.
His 16 goals in 36 appearances garnered admiring glances from Real Madrid, who are long-time admirers, with the former Lille player confessing last month that he would "consider" an offer should the Spanish champions firm up their reported €100m (Dh429m) offer. "It would be silly to dismiss Chelsea after the way they played so dominantly past year but looking at the teams, I think City and United will be up there and the teams to watch". But do I feel sorry for Chelsea because they don't have enough players?
"I have to understand Conte well".
"It was not easy to leave Real Madrid because I don't think I will return there for the third time in my career. I would have stayed for my teammates but I want a leading role and I am in the right place to have it".