Cristiano Ronaldo has paid tribute to Manchester United and then boss Sir Alex Ferguson for improving him both as a footballer and a person.

"Alex Ferguson was a father for me in football," the Real Madrid star said.

"I learned many things, not just from the coach but the players.

"I improved not just my skills but my body too.

"In the five years that I was [at United] I learned the art of football. It was a dream for me."

Ronaldo wore the No 28 shirt at his boyhood club in Portugal but described how Ferguson sprung a surprise by asking him to pull on the No 7 - a number famously worn by David Beckham, Eric Cantona and George Best.

"I remember when I left Lisbon for England, Alex Ferguson said to me, 'Listen, I want you to take the No 7'," Ronaldo, speaking at the launch of his new Nike boots, added.

"I was surprised because I knew the guys who wore that shirt. I accepted the challenge, it was great.

"It was the beginning of my success in football. It was probably one of the most beautiful moments in my career so far."