Ronaldo: Real better than United
Ronaldo will come up against his former club for the first time since trading England for Spain in a world record £80million move in 2009 when United visit the Bernabeu in the first leg of the last 16 next week.
The reigning Primera Division champions are struggling domestically this season and lie 16 points behind fierce rivals Barcelona, while the Red Devils are currently cruising at the top of the Premier League.
Despite the teams' contrasting forms, Ronaldo will be in positive mood against Sir Alex Ferguson's men although he was quick to sound a note of caution.
"I believe things will go well. In my opinion Real Madrid have a better team, but we have to show that on the pitch because United are a very united team and always have been in recent years," he said to the official UEFA Champions League magazine.
"They're a team that always do well, every year they're at the top and therefore a team we respect a lot. It will be an extremely difficult match, especially in Manchester."
It promises to be an emotional occasion for Ronaldo, who spent six years at Old Trafford.
"I actually said beforehand that I believed we would draw Manchester United," he said. "I've wanted to face them for some time. I have great memories from my time there.
"It will be a match in which I will feel a lot. I was there for six years. I have a lot of friends there, people I will see with great pleasure, it will be a match with a lot of emotions."
Ronaldo, who stated he would not celebrate should he net against United, still has much admiration for former boss Ferguson.
"He taught me the basis of football. I arrived in Manchester when I was only 18. He managed my career in the best possible way and for me he is one of the most important people in football," he added.
"I still have an excellent relationship with him and it will be nice to see him again."