The 10-time winners were out-thought, out-fought and out-worked by two-time winners Sunderland, who avenged their
league defeat by Arsenal
a week previously and have won 10 of their 15 games under Martin O'Neill.
Wenger's current team clearly lack the quality of previous squads and they will not be relishing next Sunday's Premier League visit of high-flying local rivals Tottenham Hotspur.
Phil BrownBBC 5 live pundit
"Sunderland have come up against Arsenal at the right time, there's no doubt about it. The rigours of that defeat in midweek has taken the wind out of their sails - it was a psychological blow for them. Sunderland worked harder than any team I've seen in a long, long time. It was a fantastic team performance and a well-deserved victory. Martin O'Neill said in the Premier League you're never further than two games away from a crisis. Well, those last two defeats means it's a massive crisis for Arsene Wenger. They didn't have a plan B, plan C or a plan D. They need to get that desire back because they had it but they haven't got it at the moment."
Arsenal actually looked sprightly in the opening minutes, passing and moving with an urgency that showed their determination to prove a point following the humbling in Italy.
Gervinho, back from the Africa Cup of Nations and one of five Arsenal changes, showed what the Gunners had been missing in his six-week absence with a darting run down the left.
Mikel Arteta then curled a free-kick narrowly wide as the visitors put Sunderland on the back foot and probed for an opener.
But, all season long, Arsenal have reacted poorly to even the smallest of setbacks, and so it proved again as left-back Francis Coquelin went off with a hamstring injury in the 10th minute.
He was replaced by Sebastien Squillaci, who partnered Djourou in central defence, with Thomas Vermaelen shifting across, and, from that moment on, Arsenal's back line appeared vulnerable.
They received little protection from a midfield in which Aaron Ramsey and Alex Song took knocks, but that could not excuse individual errors and a general lack of concentration and organisation.
Song was fortunate to escape after the ball struck his hand inside the penalty area before Djourou lost possession on the left and earned a caution for hauling down Craig Gardner.
DID YOU KNOW?
Arsenal allowed the opposition six shots on target this week (Milan five, Sunderland one) yet conceded six goals
The resultant free-kick from Larsson was headed out to Richardson on the left and, under minimal pressure, his drive deflected off Squillaci and into the bottom corner.
Before that, Gervinho drew a fine save from Simon Mignolet and Arsenal wanted a penalty for what looked like a perfectly-timed challenge on Robin van Persie by John O'Shea.
But those were their only clear openings in a half that saw the Gunners become increasingly ragged as Sunderland denied them time and space with an intelligent and energetic display.
The tone was set by tireless captain Lee Cattermole, but it would be unfair to highlight individuals in a team whose hunger and cohesion could not be matched by their opponents.
It was a shame that only 26,042 spectators - just over half-capacity - were at the Stadium of Light to witness their efforts.
Sunderland came close to a second before half-time - James McClean firing into the side-netting after Jack Colback's knockdown from another Larsson cross - but Arsenal held on.
The 4,000 away supporters urged Arsenal forward after the break but there was no structure to their attacks and Sunderland comfortably repelled everything thrown at them.
Wenger made a double substitution on 52 minutes - Theo Walcott and Tomas Rosicky coming on for Aaron Ramsey and the apparently injured Squillaci - but the difference was barely noticeable.
The killer blow arrived when Stephane Sessegnon robbed Oxlade-Chamberlain of possession, surged at the bedraggled Arsenal rearguard and fed Larsson on the right.
The ex-Gunner's shot came back off the post but Oxlade-Chamberlain inadvertently bundled it over the line. It summed up Arsenal's day and, perhaps, their entire campaign.
Unfair challenge on Tomas Rosicky by Jack Colback results in a free kick. Robin van Persie has an effort direct from the free kick.
Mikel Arteta takes a shot.
Shot by Thomas Vermaelen. Phillip Bardsley gets a block in.
Short corner taken by Mikel Arteta.
Corner taken by Robin van Persie from the left by-line, Phillip Bardsley makes a clearance.
Substitution Stephane Sessegnon goes off and Fraizer Campbell comes on.
Stephane Sessegnon crosses the ball, Johan Djourou manages to make a clearance.
Shot from deep inside the area by Robin van Persie goes over the bar.
Theo Walcott is ruled offside. Simon Mignolet takes the indirect free kick.
James McClean fouled by Bacary Sagna, the ref awards a free kick. Free kick crossed right-footed by Sebastian Larsson from left wing, Johan Djourou makes a clearance.
Direct strike on goal from the free kick comes in from Robin van Persie.
Booking Lee Cattermole booked for unsporting behaviour.
Free kick awarded for an unfair challenge on Alex Oxlade-Chamberlain by Lee Cattermole.
Assist on the goal came from Sebastian Larsson.
77:54 Goal scored
Goal! - Alex Oxlade-Chamberlain - Sunderland 2 - 0 Arsenal An unfortunate own goal is conceded by Alex Oxlade-Chamberlain. Sunderland 2-0 Arsenal.
Sebastian Larsson produces a right-footed shot from inside the box and hits the post.
Centre by Mikel Arteta, Thomas Vermaelen takes a shot. Save made by Simon Mignolet.
Booking The referee shows Craig Gardner a yellow card for unsporting behaviour.
Foul by Craig Gardner on Tomas Rosicky, free kick awarded.
The ball is sent over by Thomas Vermaelen.
Alex Song fouled by Stephane Sessegnon, the ref awards a free kick. Johan Djourou takes the direct free kick.
Centre by Yao Gervinho.
Free kick awarded for an unfair challenge on Jack Colback by Tomas Rosicky. Free kick taken by Simon Mignolet.
Craig Gardner has an effort at goal from outside the box which goes wide left of the goal.
Yao Gervinho is ruled offside. Simon Mignolet takes the free kick.
Unfair challenge on Tomas Rosicky by Craig Gardner results in a free kick. Mikel Arteta restarts play with the free kick.
Free kick awarded for a foul by Sebastian Larsson on Tomas Rosicky. Direct free kick taken by Thomas Vermaelen.
Corner from the right by-line taken by Robin van Persie, Simon Mignolet makes a save.
Direct effort from the free kick comes in from Robin van Persie.
Booking Sebastian Larsson receives a caution for unsporting behaviour.
Foul by Sebastian Larsson on Mikel Arteta, free kick awarded.
The ball is delivered by Sebastian Larsson, Header on goal by Michael Turner from inside the box goes harmlessly over the target.
Booking Thomas Vermaelen booked.
Free kick awarded for an unfair challenge on Sebastian Larsson by Thomas Vermaelen.
Mikel Arteta fouled by Lee Cattermole, the ref awards a free kick. Free kick taken by Mikel Arteta.
Unfair challenge on Craig Gardner by Thomas Vermaelen results in a free kick. Phillip Bardsley takes the free kick.
Bacary Sagna takes the free kick.
Substitution Theo Walcott on for Aaron Ramsey.
Substitution Tomas Rosicky replaces Sebastien Squillaci.
Foul by Stephane Sessegnon on Sebastien Squillaci, free kick awarded.
Centre by James McClean, Close range headed effort by Craig Gardner misses to the right of the target.
Free kick awarded for an unfair challenge on James McClean by Mikel Arteta. Direct free kick taken by Sebastian Larsson.
Mikel Arteta takes a long range shot clearing the bar.
Centre by Alex Song, Kieran Richardson makes a clearance.
The ball is swung over by Bacary Sagna.
Strike comes in from Sebastian Larsson from the free kick.
Booking The referee shows Bacary Sagna a yellow card for unsporting behaviour.
Unfair challenge on James McClean by Bacary Sagna results in a free kick.
The second half begins.
45:00 +2:04 Half time
Half Time The half-time whistle blows.
Close range effort by James McClean goes wide of the left-hand upright.
Stephane Sessegnon gives away a free kick for an unfair challenge on Sebastien Squillaci. Direct free kick taken by Lukasz Fabianski.
39:40 Goal scored
Goal! - Kieran Richardson - Sunderland 1 - 0 Arsenal Kieran Richardson finds the back of the net with a goal from the edge of the penalty box to the bottom right corner of the goal. Sunderland 1-0 Arsenal.
The free kick is swung in right-footed by Sebastian Larsson, Thomas Vermaelen makes a clearance.
Booking Johan Djourou receives a yellow card.
Johan Djourou gives away a free kick for an unfair challenge on Craig Gardner.
Alex Oxlade-Chamberlain fouled by James McClean, the ref awards a free kick. Direct free kick taken by Bacary Sagna.
Free kick awarded for a foul by Yao Gervinho on Phillip Bardsley. Phillip Bardsley restarts play with the free kick.
Phillip Bardsley concedes a free kick for a foul on Thomas Vermaelen. Free kick taken by Thomas Vermaelen.
Corner taken by Sebastian Larsson.
Effort on goal by James McClean from 20 yards. Alex Oxlade-Chamberlain gets a block in.
Robin van Persie takes a inswinging corner from the right by-line to the near post, save by Simon Mignolet.
Yao Gervinho takes a shot. Simon Mignolet makes a save.
Unfair challenge on Jack Colback by Alex Oxlade-Chamberlain results in a free kick. Free kick taken by Kieran Richardson.
Unfair challenge on Jack Colback by Robin van Persie results in a free kick. Kieran Richardson takes the free kick.
Foul by Craig Gardner on Thomas Vermaelen, free kick awarded. Thomas Vermaelen restarts play with the free kick.
James McClean crosses the ball, save made by Lukasz Fabianski.
Michael Turner concedes a free kick for a foul on Aaron Ramsey. Free kick taken by Mikel Arteta.
James McClean sends in a cross, Aaron Ramsey gets a block in.
Foul by Sebastian Larsson on Thomas Vermaelen, free kick awarded. Direct free kick taken by Lukasz Fabianski.
A cross is delivered by James McClean, save by Lukasz Fabianski.
Stephane Sessegnon has an effort at goal from outside the area which goes wide right of the goal.
James McClean fouled by Aaron Ramsey, the ref awards a free kick. Jack Colback restarts play with the free kick.
Inswinging corner taken right-footed by Sebastian Larsson from the left by-line, Sebastien Squillaci makes a clearance.
Substitution Sebastien Squillaci joins the action as a substitute, replacing Francis Coquelin.
Craig Gardner challenges Robin van Persie unfairly and gives away a free kick. Mikel Arteta shoots direct from the free kick.
Free kick awarded for an unfair challenge on Sebastian Larsson by Aaron Ramsey. Simon Mignolet restarts play with the free kick.
Inswinging corner taken from the left by-line by Alex Oxlade-Chamberlain.
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