United came from behind and beat the Old Lady in the Champions League midweek thanks to Juan Mata's free kick and Alex Sandro's own goal.
These came in the last five minutes after Ronaldo Juventus had advanced against his former club in Turin.
It was the first time that Ronaldo had beaten Serie A giants after joining Real Madrid in the summer.
The Portuguese striker moved to Italy after nine years in the Bernabeu and helped Los Blancos to four Champions League titles, including three in a row.
Juventus wants to return to defeat Manchester United on Sunday (19.30) to AC Milan.
And Ronaldo believes Wednesday's loss in the long term can help Max Allegri's side.
"It's never nice to lose, but maybe this defeat comes at the best possible time," said Ronaldo.
"We have a great team, we are at the top of the group and I'm sure we'll go through as group winners."
Juventus are two points ahead of United in Group H and two games to go.
Nevertheless, Manchester United boss Jose Mourinho celebrated victory in Italy by gesturing to the crowd by holding his hand to his ear.
And while this reaction upset many, Gary Neville, legend of the Red Devils, enjoyed what he saw from the former Chelsea boss.
"I thought Jose was after the game … That's why everyone loves him," Neville told Sky Sports.
"Watching the hands of fans at the end of the game … Some people do not like it – that's what I love about him, that's what I love about football.
"I think there should be a reaction and passion at the end of the game. I even liked his reaction at the end of the game against Newcastle the other week [where Mourinho spoke angrily towards a TV camera],
"For me, Jose Mourinho's best qualities were always that he was impossible when he lost, but he was impossible if he won – it was exciting to watch."