Conte has mourned the loss of Matic to bitter rival Mourinho's Manchester United.
But Mourinho fumed: “When you sell and you keep buying, then what's the problem? You are probably stronger.
“The problem is when you sell and you don't buy. People say Chelsea lost an important midfield player. But if you lose one and then you buy Bakayoko and Drinkwater for example, what's the problem?"
Mourinho also says the Blues should be favourites to retain their title.
He said: “For me the favourite is the champion, always. It doesn't mean you are going to win it, but that it is the stamp you have when you are champions, the next season you are the favourite."