Chelsea have sold the likes of Juan Mata, David Luiz, Romelu Lukaku and Andre Schurrle for big money in recent times, but Mourinho is not planning a sell-to-buy policy this summer.
“Last year I was keen to see some people leave and our club to raise some funds to buy other players,” he said after Sunday’s draw against Liverpool.
“Fundamental is to keep my players and to try to get the best out of them.
“People like Oscar. Fabulous player. I have a feeling Oscar next year can have the same evolution (Eden) Hazard had this season.”
Mourinho, meanwhile, says he will miss Steven Gerrard when he leaves the Premier League in the summer.
The Liverpool captain scored the equaliser in the 1-1 draw at Stamford Bridge, in his last encounter with the Blues before he joins MLS side LA Galaxy.
Gerrard was on the receiving end from some taunts over his slip in the 2-0 defeat to the Blues at Anfield last season, but received a standing ovation when substituted – something Mourinho was delighted to see.
“I think Stamford Bridge was fantastic,” he said.
“To get an ovation at Stamford Bridge is very special for him. It shows exactly what I’m saying – we have lots of respect for the top guys.
“I will miss him. I want my league to be always the best league. I want my league to have the best players.
“I have seen the end of amazing players and I am always hurt by that.
Luis Figo played his last game with me at Inter. Steven is leaving, Frank Lampard is leaving, Carragher – also a fantastic enemy – he left last season.
“This is modern nature. We can’t stop it but we can get great memories of our great opponents.”
Mourinho has an excellent record against Liverpool, with Sunday’s draw meaning he has lost just one of 11 Premier League games against the Reds.
The Chelsea boss hailed his players’ performance, saying it was important to focus after celebrating winning the title in their previous game.
“I think it was a good performance if you understand the circumstances,” he added.
“It’s normal that you lose a little bit of your intensity in your mental approach. But we worked hard to have the players at a positive level, and it worked. We were competing for a result.
“In the first half we were really good and I think we deserved to be in front. Then in the second half we physically went a bit down, especially because some of them are not playing a lot – Mikel, Ruben, Filipe – and some are playing too much.
“It was important for us not to lose. It was important to show Liverpool, Man Utd and to every team in the Premier League that we are champions and we have this dignity of trying to get a result.”