Graphic: Walcott's star on the wane

Such is Arsène Wenger’s endless optimism that he sees the heaviest of grey skies as a dark shade of blue, but after this second humiliating home defeat in five days even the Arsenal manager must sense the storm clouds gathering over the club. If not, then the loud booing that rang around the half-empty Emirates Stadium after the final whistle will surely have altered even his sunny disposition.

The world as viewed by Wenger must be a beautiful place in which to live, because he sees no problems, only solutions. To him, the recession is probably a good thing that forces us all to go back to basics, swine flu should be welcomed for advancing the cause of vegetarianism and Mikaël Silvestre remains a top-class central defender. Then again, even Wenger’s optimism has its limits.

In keeping with the Frenchman’s relentless positivity it is almost possible to view Arsenal’s heaviest home defeat since 1977 as a good thing, if only for revealing the extent of rebuilding required before they are capable of challenging for trophies again. All of Arsenal’s biggest faults were in evidence, with a combination of woeful finishing and comical defending enabling Chelsea to stroll to their biggest victory in this part of North London since 1960 and secure a top-three finish in the Premier League.

The first step to recovery in any failing enterprise is an honest recognition of your faults, however, which has never been a Wenger strength, as was demonstrated by his postmatch analysis. He was once mocked for being myopic, but his condition is now gripped by delusion.

“It was not a 4-1 defeat today,” Wenger said. “You can be very positive or very negative. It’s a major disappointment to lose 4-1, but going forward we had a very interesting game and created plenty of chances. That was never a 4-1 game.

“We should have been 2-0 up before they scored. We made a mistake and were one down, but we missed seven or eight clear-cut chances and every mistake we made was punished because we were playing a team of quality. Three months ago everybody said we’d finish tenth and they’d have been happy to have finished fourth.”

In his programme notes Wenger had been even more indulgent, describing the two early goals his side conceded against Manchester United last week as an “accident” that should be disregarded, and arguing that Arsenal showed themselves to be equals to the champions over the two legs. Such a claim was eye-catching in print and was made to look utterly ludicrous out on the pitch, as the home side imploded.

Arsenal did start the stronger, as Wenger had claimed, with Theo Walcott missing four good chances in the first 20 minutes, but then proceeded to self-destruct in a manner that only they can.

Accident-prone does not even come close to describing recent defensive efforts of a side that have conceded 11 goals in three matches against Liverpool, United and Chelsea.

Many of Arsenal’s problems stem from the knee injury that ended William Gallas’s season against Villarreal last month, not least because it facilitated the return of Silvestre to the side. The French defender was culpable for Chelsea’s first two goals, being outjumped by Alex at a free kick controversially won by Didier Drogba and failing to close down Nicolas Anelka after he had skipped past Samir Nasri, although Lukasz Fabianski should have done better with his shot.

Chelsea’s third was the kind of aberration that seems only to happen to teams that are struggling, with Kolo Touré diverting Ashley Cole’s cross into his own net, while they were also hopelessly exposed for the fourth as Florent Malouda tapped in after Anelka had hit the post. Wenger must sign an experienced central defender as a matter of urgency this summer, particularly as Touré remains unsettled, although the same situation faced him last summer and all he came up with was Silvestre.