Manchester United keeper Edwin van der Sar believes Cristiano Ronaldo is being "driven on to greater heights" by the negative reaction towards him from opposition fans.

Ronaldo has been the target of the boo-boys ever since the incident in the Portugal-England World Cup quarter-final which ended with Wayne Rooney being sent off.

But the winger has been in superb form this season and produced another fine display in Saturday's 3-0 win at Aston Villa which ensured Sir Alex Ferguson's side entered Christmas at the top of the Barclays Premiership.

Now he will look to help United stay ahead of Chelsea by winning successive home games with Wigan and Reading.

Van der Sar said: "Cristiano is getting better and better. He is still only young but he is more mature now as a footballer.

"He has loads of qualities with the ball but is more aware now in terms of his positional play, the runs he can make, the other players who make runs for him, and of creating space for other players.

"I think it is his most productive season so far. He is scoring more goals and delivering more crosses. He has been excellent for us."

Van Der Sar added: "I wasn't in England after what happened with Cristiano at the World Cup but I can imagine what the papers and TV were saying.

"It was a country versus country situation and you do the best for your own country.

"The United fans have stuck with Cristiano and I think the opposing fans see the quality he has and the joy with which he plays the game.

"He will get some occasional booing but that's all right. I thank that only serves to drive Cristiano onto even higher ground, to greater heights.

"Cristiano hasn't let what happened and the reaction affect him at all. He is a very strong guy and has shown that this season."

Ronaldo's double blast against Villa took his goal tally for the campaign to eight and Ferguson is confident he can double that tally before the end of the campaign.

His demands for a greater goal return from Ronaldo have answered in a positive vein.

Ferguson said: "Cristiano could easily get us over 15 goals this season and he is certainly capable of achieving that.

"He is unbelievable and in great form. He is as good as anyone in the country. He is having a magnificent season for us. He shows great courage and strength."

Van Der Sar stressed the need for United not to relax in the forthcoming home games after bouncing back in style at Villa Park from the shock reversal at West Ham.

He said: "It was great to go into Christmas at the top of the table, certainly better than being second.

"We have two home games coming up and you would expect six points from those matches - and that is not being disrespectful to the other teams.

"We need to keep winning our home games. Away from home, with the exception of the game at West Ham, we have been quite solid."

Wayne Rooney could be restored to the United starting line-up against Paul Jewell's side after only being a substitute at Villa after a midweek family bereavement.

It was the first time he had not started a league game for United since his early season three-match ban and Ferguson is mindful of keeping his strikers fresh.

He said: "I have to think about that when resting the forwards because they have been bearing the brunt for us all of the time.

"For the defenders it is much easier but for the forwards who have to produce quality, you have to be careful with the endurance side of things."