Mourinho has offloaded the likes of Romelu Lukaku, Kevin de Bruyne, Juan Mata and Andre Schurrle for a combined fee reported to be in excess of £100 million since returning to the Stamford Bridge hotseat in 2013.
Lukaku left for Everton for a reported £28m in July having spent the previous Premier League campaign on loan at Goodison Park, but Mourinho insists the Belgium striker has nothing to prove when the sides meet on Wednesday.
"I think he proves every weekend that he is a good player," he said. "He has nothing to prove to us
"We know he is a good player, we know Schurrle is a good, we know De Bruyne is good, we know Mata is good.
"That's football, that's life, that's the market.
"Sometimes it is the players' wishes to be at clubs where they become first choice.
"The important thing is, if [Lukaku] is happy, that's good. From what I know from him the couple of months we were together, he is happy now."
Chelsea's most recent high-profile departure was Schurrle, who joined Wolfsburg for a fee though to be around £22m towards the end of the last transfer window.
When it was put to Mourinho that Chelsea always achieve a sizeable return for their players, the Portuguese responded: "It's because they are good. We don't sell garbage, we sell top players.
"We sell top players, we get top fees. That's normal."
Chelsea host Everton in the Premier League on Wednesday, having won the reverse fixture 6-3 in August.
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