Manchester United boss Sir Alex Ferguson has challenged new signing Zoran Tosic to follow Cristiano Ronaldo's example.

Ronaldo was only 17 when he came to England from Sporting Lisbon. United are hoping to nurture 21-year-old Tosic in the same way, following his estimated £10million move from Partizan Belgrade.

It is asking a lot of Tosic to have quite the same impact. But Ferguson's commitment to the excellence of youth ensures the young Serbian winger will be given every opportunity to fulfil his enormous potential.

"We would like everyone to turn out like Cristiano," said Ferguson.

"There is a difference - because Ronaldo had this fantastic dribbling ability, whereas Zoran is more straightforward.

"But the point is we are planning for the future - and the challenge any young player should set himself, no matter which club he is with, is to get to the very top.

"We are all proud of Cristiano achieving the status he has. But it is a two-way street.

"The player must have the personal ambition, the desire and drive to succeed. But he also owes a lot to Manchester United for nurturing and encouraging him in the proper way at the right times."