Kakuta made his debut and looked completely at home in the top flight. He was originally suspended for four months when FIFA imposed their transfer ban on the club in September for inducing him to breach his contract with Lens two years ago.
But the Court of Arbitration for Sport suspended the bans until the outcome of Chelsea's appeal has been heard in full and Kakuta seized the chance to shine when he replaced Nicolas Anelka in the second half.
"Kakuta has a lot of talent and he showed that in 30 minutes," said Ancelotti.
"He is young and he has to improve and work. After two or three weeks of his ban he had some difficulty because he is very young. But we had him train with the first team and now he is happy. I hope he will do better in the future."