The Brazil international scored his side's first goal in the 2-1 win at Crystal Palace on Saturday as Chelsea maintained their five-point lead at the top of the Premier League.
And Mourinho was gushing in his praise of the 23-year-old after Chelsea extended their unbeaten start to the new season
"Oscar did fantastic against Arsenal and again [at Palace]," said Mourinho.
"He's not a number 10 that plays with the ball on his feet; he is a number 10 that looks back, looks to the side, analyses the game and sees where the team need him to move to get the ball and where the team needs him to move to create balances.
"For example, in the first half when they had [James] McArthur playing man-to-man with [Cesc] Fabregas, I was so happy with that.
"Fabregas was taking McArthur from the central area and Oscar was dropping back to play. Oscar and [Nemanja] Matic controlled the game completely for us.
"Oscar, at this moment, is not a number 10. He had an evolution - a mental, tactical evolution that allows him, in my opinion to be a fantastic player.
"People forget that he arrived here two years ago and he is still so young."
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