Ryan Giggs's bid to be the new David Beckham lasted precisely an hour. The Welshman's clean strike from a 30-yard free-kick looked like being the only talking point of a drab opening match until Sir Alex Ferguson introduced 18-year-old Cristiano Ronaldo to enliven proceedings.

The coltish Portugal player certainly did that. Manchester United blew away Bolton Wanderers with three goals in the last half-hour and could have had more. No one was talking about Beckham at the end of the match and not even a second goal from Giggs could promote him back to top billing.

The only topic of conversation was a sensational debut by a player who can do precisely what Beckham could not - ghost insolently past defenders and produce the unexpected - and at £12.5 million cost half of what United received from Real Madrid for the England captain.

'It was a marvellous debut,' Sir Alex Ferguson purred. 'I thought the pace was too slow in the first half and I knew Cristiano would add penetration.' Even Sam Allardyce could not find anything grudging to say. 'He was different class, he looks a very exciting player and his introduction was crucial,' the Bolton manager said.

'I felt it was time to change our team around,' Ferguson had explained beforehand, evidently feeling the need to justify his summer clearout. 'David [Beckham] contributed hugely to our success and has a place in the history of the club that will last for ever, but we must never stand still. Seba [Veron] played some marvellous games in European competition, but I think he found the Premiership difficult.'

Fair enough, and Chelsea take heed, but United fans were made to wait to see the future. For an hour it looked as if far too little had changed, with Roy Keane and Nicky Butt in the middle, Paul Scholes and Ole Gunnar Solskjaer on the wings and Quinton Fortune filling in rather uncomfortably at left-back. United looked far from dynamic.

Giggs spent most of the first half attempting to play off Ruud van Nistelrooy and suffering from the same lack of service and when he did get an open invitation, after 25 minutes, he fluffed it. The old Giggs would have accelerated purposefully towards goal when Florent Laville's mistake let him through; the new one appeared to lack the confidence to take on Jussi Jaaskelainen and squandered the opening by trying to lay the ball square to no one in particular.

Until Giggs redeemed himself, Bolton had looked as likely to take the lead. United had not managed to split their opponents' defence as cleanly as their visitors did through Jay Jay Okocha's pass and Kevin Nolan's sharp turn in the 18th minute and were grateful when Nolan took far too long to appraise the situation and fire in a shot. Kevin Davies shot narrowly over the bar five minutes later before Van Nistelrooy, in almost his only contribution of note in the first half, went down under N'Gotty's innocuous-looking challenge in what used to be known as Beckham territory.

No Beckham now, of course. No Veron either. Yet although Giggs's finishing of late has been far from menacing, the Welshman assumed responsibility and beat Jaaskelainen via a rebound from the goalkeeper's left-hand upright. A muted roar went up - half relief, half disbelief.

Possibly as bored as everyone else in the second half, Ferguson flicked a switch and illuminated Old Trafford. Bolton sent on Youri Djorkaeff, com plete with facemask protecting a fractured cheekbone, but United topped that by introducing their new capture from Sporting Lisbon. 'There's only one Ronaldo,' sang the same crowd responsible for giving a standing ovation to some Real Madrid player last season.

Once Eric Djemba-Djemba began warming up, there was definitely more interest in the dugout area than the increasingly disjointed event on the pitch. The Cameroon midfielder duly came on for Solskjaer, a bold change by Ferguson with only one goal in the match, and was immediately eclipsed by events on the left flank, where Ronaldo was wasting no time in winning over his new public.

Bolton were warned by one skipping dribble down the left. Then, when Ronaldo produced more fancy footwork to cut into the penalty area past Nicky Hunt, a bemused Nolan could only tug him back by the shirt. A full-length save by Jaaskelainen denied Van Nistelrooy the penalty, but no matter, Ronaldo was back again two minutes later, crossing from the left for Scholes to set up Van Nistelrooy. Jaaskelainen could not hold the shot and Giggs was presented with the simplest of tap-ins for his second goal.

Djemba-Djemba got into the act 13 minutes from time, passing forward for Van Nistelrooy, but instead giving Scholes the opportunity to round Jaaskelainen. Then, just when it looked as if Van Nistelrooy might have to be content with scoring in just 10 consecutive competitive matches, his chance to establish a record arrived via Keane and Diego Forlan in the 87th minute. The Dutchman buried it with a venom.

United are clearly not standing still, and Kleberson is still to come.

MAN OF THE MATCH

Cristiano Ronaldo : Paul Scholes probably deserved it, Ryan Giggs scored the first two goals, but everyone left Old Trafford talking about a sensational half-hour from United's new 18-year-old midfielder. David who?