Sir Alex Ferguson has challenged Cristiano Ronaldo to maintain his form this season for the rest of his career.

The Portuguese winger was instrumental in helping Manchester United break Chelsea's dominance in the Barclays Premiership, and the 22-year-old has also swept the board in the end-of-season awards, adding the Football Writers' Association accolade to the PFA Player of the year and Young player of the year awards.

"I hope he goes on to develop himself to be established as the best footballer in the world," The United manager said. "To do it for a long time is another challenge for the boy and I think he will do that."

Ryan Giggs, who was honoured by the FWA at their tribute night earlier in the season, added to the plaudits, remembering how Ronaldo teased his United team-mates just before arriving at Old Trafford in a pre-season friendly against Sporting Lisbon.

"I was sitting on the bench in Portugal nearly four years ago. I sat there in Lisbon laughing my head off," Giggs said. "There was a kid called Ronaldo taking the mick out of our lads on the pitch. He had all the tricks and stood out as a special talent.

"We were talking about him on the flight back to Manchester, so there was genuine excitement when we heard we might be signing him.

"Like me, he was a winger but I didn't feel threatened by the thought of him arriving at Old Trafford, in fact my feelings were the exact opposite to that," Giggs added.

"I was just delighted to see him arrive at United when the deal went through. I welcomed the signing of a special talent at the club - and that is exactly what he has proved to be."