Ferguson said the Brazil international is destined to become one of the world's best full-backs, after the 21-year-old signed a new four-year deal with the club.

Rafael joined United from Fluminense alongside twin brother Fabio in 2008, but has yet to secure a regular first-team berth.

However, his manager said the 21-year-old can go on to become one of the best in his position given his development since joining the club.

Ferguson told the club's official website: "Rafael has all the attributes to become one of the best full-backs in the world and I am delighted he has signed a new contract.

"The boy has developed immensely since joining United, his energy and enthusiasm are a joy to watch.

“Rafael is one of the club's brightest young prospects; he has no fear of playing and has great belief in himself."

The right-back thanked his manager for his support and spoke of his desire to continue bringing trophies to Old Trafford.

Rafael said: "I love playing for Manchester United, there is a great team spirit here and a real desire to win.

"I would like to thank Sir Alex for his belief in me and I would also like to thank the fans for their support.

"My time here has been unbelievable; winning two league titles, a league cup and a Club World Cup has made me hungry for more trophies."