The England striker, who will now be sidelined following his dismissal against FC Porto in the recent Amsterdam tournament, was irresistible scoring twice and playing a major role as Louis Saha, Cristiano Ronaldo and an own goal from Fulham's Ian Pearce completed United's goal haul.

With Heidar Helguson's deflected shot off Rio Ferdinand providing the only blemish on an almost perfect afternoon for United, any doubts about how they cope with the loss of Ruud van Nistelrooy were quickly blown away.

United's pre-season campaign had been marred by the sendings off of Rooney and Paul Scholes in Amsterdam, the injury to 18 million pounds midfielder Michael Carrick, and repeated failures in the transfer market.

But any early gloom was quickly forgotten as United shredded a desperately unimpressive Fulham defence with a devastating four-goal blitz inside the opening 20 minutes to serve notice on champions Chelsea that this year's title race will be a more closely fought contest.

And with Rooney and Ronaldo showing their spat when England met Portugal in the World Cup quarterfinal is now well and truly behind them, an air of optimism descended on Old Trafford long before half-time.

Ferguson stills hopes to add more new faces to his squad with Bayern Munich's Owen Hargreaves the principal target, but this win added support to the United manager's claim that his squad is already sufficiently strong to mount a realistic challenge in the league.

With just seven minutes gone, Ryan Giggs drilled a left wing cross into the Fulham box where Saha was allowed to head home unchallenged from just six yards.

Then seven minutes later it was Saha's turn to act as provider, sending in a low cross towards the near post where Pearce turned the ball past his own keeper under pressure from Rooney.

Within two more minutes, the game had turned into a rout as Rooney pounced on a loose ball to make it three and in the 19th minute it was the striker's cross that allowed Ronaldo to volley home at the far post.

Helguson's fortunate deflected effort gave Fulham pride in the 40th minute, but normal service was restored when Rooney slotted home just after the hour to make it five.

Fulham's dreadful away form last season almost pushed them into the relegation zone and with manager Chris Coleman insisting out-of-favour playmaker Steed Malbranque will never play for the club again, another long hard campaign awaits.