Arsene Wenger emerged from the dressing room with the face of a man who had just inflicted some serious damage.
No more the tolerant, protective figure who nurses his charges through their weekly tests and tribulations.
This time, home truths had been told and blood had been spilled.
Stop gap: Arsenal keeper Manuel Almunia saves penalty
Here in north London, theywere trying to recall when Wenger came out with lines like 'I didn'trecognise my team today. we were collectively poor. we got whatwe deserved. it is unexplainable'.
There wasn't a single expletive and the voice was never raised. But coming from Wenger, it carried the force of a diatribe.
And what gave his criticisms a cutting edge was the knowledge that he had brought some of the troubles upon himself.
Over the past year or more, it hasbecome a wearisome cliche to suggest that Arsenal lack a talented,efficient, dependable goalkeeper.
After Manuel Almunia's latestexhibition, the need is more pressing than ever. Wenger refused tocondemn individuals, insisting his defence had made some massivecollective errors.
Treble chance: Jerome Thomas shoots past Laurent Koscielny to score their third goal
But he knew, as 60,000 others knew,that the bulk of the blame for this extraordinary defeat should be laidat his keeper's creaking door.
Albion's second goal, the success which made them believe that victory was achievable, was a grotesque mistake by Almunia.
It emerged from the 52nd minute whena ball was slickly played into yards of space down the right andGonzalo Jara moved on to the opportunity.
He assessed his options and decided to gamble on crashing a shot at the near post.
A more confident, more competentgoalkeeper would have stifled the drive. Almunia stooped arthritically,lost his bearings and somehow scooped the ball into his own net.
It was the kind of error whichbreaks a team's heart. Some 20 minutes later, he handed over the thirdgoal and, effectively, the game.
Chris Brunt worked his way acrossthe Arsenal defence and moved wide to the right. Amazingly, the keeperelected to follow him. He seemed to think about changing his mind, butit was far too late, and he was stranded yards outside his goal whenthe cross came over.
As Jerome Thomas clattered the drive, Almunia was barely in the same postal district. It was another calamitous error.
In truth, the inadequacies of Arsenal tended to overshadow the genuine virtues of a resolute Albion side.
Their manager, Roberto di Matteo,insisted that they had gone into the match believing they could win,and their positive approach endorsed his view.
Remember me: West Brom's Jerome Thomas celebrates scoring against his former club
Predictably, West Bromwich hadattempted to impose themselves physically at the start, but theirefforts were largely within rules and reason.
Jonas Olsson was booked for a reckless lunge at Emmanuel Eboue on eight minutes, but it was scarcely an outrage.
So Arsenal played their football, Albion did their work and the crowd waited for Arsenal to break the stalemate.
They went close a time or two, andnever closer than Andrey Arshavin's effort which slapped against apost, but they could never find the pass to strip down the defence.
And when the really important breakwas made, it was Albion who made it. Brunt, a significant figure inmidfield, ran into space and played a pass through to Peter Odemwingie.
Almunia came surging out, sprawled obstructively and brought down the striker for the clearest penalty.
Brunt took the kick, but struck the ball without power or intent, and Almunia practically fell upon the effort.
Hard to watch: Arsene Wenger
Equality at half-time was something Arsenal scarcely deserved, but it offered them the chance to set things straight after the interval. In fact, they never looked like taking it.
In five minutes, Albion were ahead.
Thomas, attacking on the left, went round Bacary Sagna rather too easily.
The cross was cut back, and Odemwingie reacted half a yard ahead of the rest to take his chance.
It was then that Almunia played his disastrous hand. It might have been redeemed late on. With 15 minutes remaining, Sami Nasri picked his way through the tackles for a tidy goal.
Then as the game went into added time, he repeated the feat to raise hopes of a point which would have been ill-deserved.
In those last, hectic moments, a host of chances arrived, and all were missed. Justice was done, and one of the shocks of the young season was complete.
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