Watford 1 Manchester United 2: Manchester United stayed at the top of the Premiership thanks to their third straight victory - and gave newcomers Watford a tough lesson about life at the top.

With the match level at 1-1, Watford missed a marvellous chance to take the lead, and were promptly punished when Ryan Giggs - outstanding throughout in the visitors' midfield - seized on substitute Matthew Spring's wayward back pass to score the winner after 51 minutes.

Mikael Silvestre had earlier finished off a brilliant move involving Giggs and Louis Saha to put United in front in the 13th minute, but this Watford side possess an unquenchable competitive spirit, and they overcame their clear technical inferiority to equalise through Damien Francis 21 minutes later.

This victory puts United six points clear of champions Chelsea, who are already under pressure and play at Blackburn tomorrow.

Michael Carrick made his first league start for United since his £18.6million move from Tottenham earlier in the summer, while Richard Lee started in goal for Watford as Ben Foster was ineligible under the terms of his loan move from Old Trafford.

Watford began with the same purpose and tenacity that characterised their 1-1 draw with West Ham in midweek and, briefly, Sir Alex Ferguson's side looked rattled.

But having negotiated the opening stages, United began to make their superior passing and movement tell.

Carrick's curling cross in the 10th minute forced Lee to back-pedal quickly and tip over, and from Ryan Giggs' resulting right-wing corner Cristiano Ronaldo - predictably booed by the home supporters - headed just wide of the left post from six yards.

United had to wait only two more minutes before they took the lead with a goal of beautiful simplicity.

Giggs made a menacing run from inside his own half before releasing Louis Saha, who slipped the ball to his left for Silvestre to burst into the penalty area and drill an angled, left-footed shot just inside the right post.

In the 27th minute, Lee made a stunning save to deny Saha, who found space at the near post to direct Giggs' fiercely swerving corner towards goal with his head.

Watford boss Adrian Boothroyd, perhaps recognising the visitors' superiority in midfield, brought off wide man Hameur Bouazza and sent on Spring to give his team more bite and resolve in the centre of the pitch.

The move paid off within three minutes as Watford - who had shown superb spirit when United were at their most dangerous - equalised in the 34th minute.

The impressive Ashley Young tricked his way past Silvestre on the right and drove the ball low across the face of goal where Francis, whose run from midfield had gone untracked, tapped in his second goal in three matches since his summer move from Wigan.

Watford made a bright start to the second half - but were quickly given a demonstration of the ruthlessness which is required to survive and prosper in the Premiership.

In the 51st minute, Watford should have taken the lead - and paid the ultimate penalty when they fell behind 60 seconds later.

Only Dan Shittu and Francis will know why they failed to pounce after Darius Henderson had steered Marlon King's deflected free-kick back across the face of the United goal, with keeper Edwin van der Sar stranded.

The pair - perhaps believing they were off-side - simply stood and watched instead of intervening, and they were quickly punished for their error by Giggs.

Collecting Spring's under-hit back pass, the Welshman evaded goalkeeper Lee with remarkable ease before steering the ball into the empty net with his right foot.

Watford won a number of free-kicks and throw-ins in dangerous areas, as well as corners, but they could not make them count as United held firm in defence.

The visitors almost netted a third with 18 minutes remaining, but Watford keeper Lee reached Ronaldo's through-ball a split second before Park.

While Watford pressed forward, United would always look dangerous on the break, and Lee denied Ronaldo once more with an assured save from the ex-Sporting Lisbon man's left-footed strike from 20 yards.

Saha should have made the game safe in the 88th minute after being supplied superbly by Giggs, but Lee - who had done his cause no harm - was quickly out of his goal to block the France international, while at the other end Shittu fired over in stoppage time.