Ronaldo paid tribute to the United fans and claimed he will "never forget" the ovation that greeted his appearance prior to kick-off at the Theatre of Dreams, his first since leaving for Spain and the Santiago Bernabeu in 2009.
"It was an unbelievable night, a very emotional night and what the supporters did for me was massive," Ronaldo told MUTV. "I am never going to forget that moment. The only words I can say are that it was unbelievable.
"For one side I feel happy, for Madrid to go through to the next round, but for the other side I feel a little bit sad because it is not easy to forget this home. I played for six years here and the people were very nice to me. I came here like a child. It was quite a strange feeling.
"Not just for this game, but the first game too. I felt a little but shy in my game and I have feelings which I can't explain. I am happy because Madrid got through, I defend my colleagues and I play for Madrid so I try to do my best all of the time."
Ronaldo, who scored 118 goals in 292 appearances over six trophy-laden years with United, entered the home dressing room after the match to speak with his ex-teammates, consoling them on the result.