The Uruguayan had only just entered the fray when he pounced three minutes into injury time to lash home left-footed a perfect pass from fellow replacement Juan Sebastian Veron.

The devastating blow left Chelsea down, and probably out, of the title race and in turn piled the pressure back on Arsenal, who go into Sunday's derby with West Ham only two points better off than their bitter rivals.

Petit then drilled a rising effort inches wide of compatriot Fabien Barthez's left-hand post as Roy Keane and Phil Neville came a clear second in the scrap for midfield supremacy.

The one downside for Chelsea was that none of their early openings fell to Jimmy Floyd Hasselbaink. Indeed, the Dutchman was only on the pitch for 15 minutes before limping off to be replaced by Gianfranco Zola.

In talks with Barcelona, the striker may well have kicked his last ball for the Blues but could not have made a more inauspicious exit had he planned it himself.

But Zola has been the pivotal figure in Chelsea's surge this season and rightly back in Claudio Ranieri's line-up, he helped lay on the deserved opener.

Petit was quick enough to rob Phil Neville in the middle and picking up a return from the little Italian, the former Gunner split a static backline for Gudjohnsen to flick the finest of finishes over Barthez.

It was his fifth goal in as many games and lifted an entire stadium. The roof almost came off completely within six minutes of the restart as more Chelsea dozing and another excellent Beckham delivery saw Ole Gunnar Solskjaer swivel smartly, only to see his snap-shot cannon back off a post.

Cudicini then came into his own, somehow clawing a Ruud van Nistelrooy header aside before the Dutchman, who had also blazed an ugly volley way over the top, came off to be replaced by the almost-forgotten Forlan.

After finally breaking his duck and then finding the net eight times he has found himself sacrificed for the Scholes-van Nistelrooy pairing, but pushed rather than nudged Ferguson's memory with a fervent late cameo.

His first impact was a low, bobbling drive that Cudicini did well to keep out, but with Chelsea failing to capitalise on a couple of late breaks, the stage was set for the little Uruguayan to claim what could be the biggest goal of the season.

Veron followed him into the action and as soon as he got on the ball, he looked up bent the pass in behind the Chelsea centre-backs where it bounced once before being lashed, ruthlessly into the roof of the net, with Cudicini clutching air.