Antoine Griezmann punished Arsenal's lax defence late on as 10-man Atletico Madrid salvaged a draw from the Europa League semi-final first leg at Emirates Stadium.
The visitors were on the back foot for almost the entire game after defender Sime Vrsaljko was dismissed for two yellow cards in the first 10 minutes.
With Atletico's furious manager Diego Simeone sent to the stands shortly afterwards, the Spanish side survived unscathed to half-time, with Alexandre Lacazette clipping the post with a half-volley the hosts' best chance.
Lacazette nodded in Jack Wilshere's cross just after the hour to apparently edge the Gunners closer to a Europa League final send-off for outgoing manager Arsene Wenger.
But with eight minutes remaining, Griezmann latched on to a long ball forward, shrugged off Laurent Koscielny and stabbed into the net at the second attempt for an away goal to swing the tie Atletico's way going into the return leg in Madrid next Thursday.
Arsenal's fans were left ruing a familiar combination of wasteful finishing and costly lapses in concentration as the teams departed to a muted response in Wenger's final home European game.
Their team now must breach an Atletico defence that has conceded just four times at home in La Liga this season to have any hope of extending Wenger's 22-season spell in charge to the final on 16 May.
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Atletico's early outbursts
In contrast to Arsenal, Atletico Madrid's defensive discipline has served them well in recent continental campaigns, grinding out victory in four of their five European semi-finals over the past nine seasons.
But the Spaniards' usual pragmatism deserted them as they self-combusted in the opening 13 minutes.
Croatian right-back Vrsaljko was booked as he caught Wilshere late in the second minute and, instead of showing the requisite caution, blundered into Lacazette with his studs up eight minutes later.
So early in the contest, Atletico may have expected referee Clement Turpin to limit punishment to a stern and final warning.
But the 35-year-old Frenchman judged the challenge rather than the occasion and showed Vrsaljko a justified second yellow.
Simeone was exasperated by that decision and incensed by Turpin opting not to book Hector Bellerin shortly after. The Argentine was dispatched to the stands after aiming a stream of invective at the official.
Atletico in their element
If any side is suited to surviving such a precarious situation though, it is Atletico.
Midfielder Thomas Partey slotted back into defence, forward Griezmann dropped deeper and their whole side set about absorbing Arsenal's pressure and running down the clock.
The visitors rode their luck at times, with Lacazette grazing the post with an awkward half-volley, but had chances of their own in the first half with Griezmann thumping a fierce shot straight at David Ospina.
As Simeone stood impatiently in a gangway high above and his assistant German Burgos orchestrated from the sidelines, their side threatened to throttle the life out of the game.
The tightest defence in La Liga - with only 18 goals conceded in 34 games - was finally undone as Wilshere dug out a cross and Lacazette hung above Lucas Hernandez to score his 16th of the season.
With Griezmann lurking though, Atletico always retained the power to land a sucker punch.
The France international was played onside by dawdling Nacho Monreal before he hustled Koscielny into a swiped, unsuccessful clearance and applied the finish to spark delirium in the away section.
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Aaron Ramsey's header was brilliantly pawed away by Jan Oblak as Arsenal pushed in vain to re-establish their lead but, given the weight of the away goal, it may not have unseated Atletico as favourites to progress.
Wenger has twice lost in European finals with Arsenal, missing out in a penalty shootout against Galatasaray in the 2000 Uefa Cup final, before being broken down by Barcelona in the Champions League final six years later.
It will require one of Arsenal's great European displays to take him to a third.
The Gunners may take heart from London rivals Chelsea, who won 2-1 at the Wanda Metropolitano in September.
Man of the match - Diego Godin (Atletico Madrid)
Score-draw specialist Simeone
- Atletico Madrid have drawn 1-1 on each of their past three visits to England - against Leicester City in last season's Champions League quarter-final and at Chelsea in this season's group stage.
- Atletico Madird have been victorious in seven of their nine two-legged knockout contests against English opponents.
- Arsenal have lost all of the past three two-legged ties against Spanish opposition - all to Barcelona in the Champions League.
'The worst possible result considering the game'
Arsenal manager Arsene Wenger speaking to BT Sport: "Looking at the performance and the way the game went, it was the worst possible result for us, but we have to go there in a positive mood and qualify.
"Of course it feels like an opportunity missed. We could have qualified tonight but it didn't happen. Their keeper made a lot of saves and they showed their quality by scoring with one chance.
"What matters is that we go there with the belief to do it."
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