After Ronaldo had fired Juventus in front, United turned the game on its head in the final five minutes with two quick goals.
An own goal from Alex Sandro sealed an unlikely victory for United in Turin, and Ronaldo was disappointed to see his side lose after dominating the game.
Juventus were on top from the first whistle, created several excellent chances and Ronaldo thinks Jose Mourinhos tactics relied completely on set-pieces.
I was happy for the goal, but are a little bit disappointed because we should win the game easily, [by] three or four goals, Ronaldo said after the game.
Manchester didnt do much, in my opinion. They create two chances at set-pieces. English teams always looking for the set-pieces.
Cristiano Ronaldo scores first Champions League goal for Juventus!
And what a way to do it!
— Football on BT Sport (@btsportfootball) November 7, 2018
But we learned from out mistakes and we are still top of the group, so we are good.
Juan Mata scored direct from a free-kick, before Ashley Youngs cross from another set-piece was diverted into the Juventus net by Sandro.
Ronaldo scored a sublime volley in the forwards first Champions League goal as a Juventus player.
The former Red Devil celebrated by lifting up his shirt and showing off his abs, but it was his former side that took home the three points.
The result cut the gap between Juventus and United in Group H to two points, and the Red Devils could still finish top if they win their final two matches and the Italians drop more points.