Manchester United boss Sir Alex Ferguson has described Cristiano Ronaldo's progress as "absolutely amazing".

"It is always difficult when you sign a boy of that age," he said.

"He has to grow and develop and also get used to living in another country, which is never easy.

"Under those circumstances, the rapidity of his rise has been absolutely amazing.

"Now we are seeing a maturity in his performance of someone in their mid-20s."