Chelsea hosts Everton on Wednesday, with Belgium international Romelu Lukaku returning to the club following his 28 million-pound summer move.
That was one of a series of big outgoing deals for Chelsea that also included Juan Mata's move to Manchester United, David Luiz's sale to Paris Saint-Germain, and Kevin De Bruyne and Andre Schurrle's switches to Wolfsburg.
When asked why that was at a news conference on Tuesday, Mourinho replied: "Because they are good. We don't sell garbage. We sell top players.
"Mata: world champion. Schurrle: world champion. Lukaku: one of the best young strikers, fantastic prospect. De Bruyne: one of the best young players also. Both playing for a very important national team, probably one of the best national teams for the next decade. We sell top players and we get top fees. If we didn't get top fees, we wouldn't sell them because we want to keep them."