Ancelotti says Vinicius Jr is 'back to his best' for Real Madrid
The Brazil international, who assisted England midfielder Jude Bellingham's goal, was named man of the match as he helped Madrid keep three points clear at the top of Group C.
Vinicius sustained a hamstring injury in August and was sidelined for a month.
"He's back to his best. He got the goal, which was ruled out by the narrowest of margins, and he made two assists for Rodrygo and Bellingham," Ancelotti told reporters. "He's back, and he's back in form. He made the difference today.
"They (Bellingham and Vinicius Jr) work really well together with the ball and without it. We have to improve there but they're both doing a great job."
Real Madrid, the record 14-time Champions League winners who lead in the La Liga with 25 points after 10 matches, play arch-rivals Barcelona on Saturday. Third-placed Barcelona trail Madrid by just one point.
"After this game, we know exactly what we need to do - everything we can to win it," Ancelotti said.
"We have time to get ready for it. We're heading into this incredibly important game full of excitement."