Arsenal had the chance of a lifetime or two, as they were handed the golden opportunity after Šime Vrsaljko lost his head, twice in a matter of 8 minutes to get sent off for two yellow-card offences.
The Gunners then piled on the pressure but the Atletico defence didn't crack until the hour mark when Alexandre Lacazette rose to manoeuvre the ball into the back of the net with a towering header.
Arsenal knew that they probably needed another goal to get some breathing space before they have to do it all over again in Madrid in a week's time.
However, their failure to put away the chances and the tie to bed, despite the numerical advantage, will most likely come to haunt them as Antoine Griezmann got his side an invaluable away goal after a comedy of errors by the infamous Arsenal defence.
On that note, here is a look at three things that went right for the side from Madrid:
#3 Arsenal's failure to put away their chances
The Gunners couldn't believe their luck when they were handed, rightly so, a numerical advantage with less than ten minutes on the clock. What followed was an exercise in patience for the fans at the Emirates as they contrived to pass up chances after chance before they finally troubled the scorers.
With all of Atletico's men behind the ball for what seemed like the entirety of the game, Arsenal weren't able to find as much time and space as they would've liked on the edge of the opposition box to be able to pick that intricate ball through that they so often crave.
They did, however, manage to get their wing-backs in support and made the numbers count as both Nacho Monreal and Hector Bellerin kept finding themselves in behind the Atleti defence but were unable to find a telling cross. Jack Wilshere had better luck with crossing as he managed to find the Frenchman to get the scoring underway.
They quickly reverted to not finding the back of the net in the following half an hour or so and the Spaniards made them pay as they managed to get a priceless away goal.
Arsenal went out of their way to not make their numerical advantage count after Atletico had gone out of theirs to hand the hosts the initiative.
#2 Jan Oblak was a beast in goal
One of the most talented men with gloves in world football at the moment, Jan Oblak, was Atletico's saviour on the night with a number of remarkable saves to help his side go into the second leg with what could prove to be an overwhelming advantage for the side from north London.
As crucial as Greizmann's goal was on the night, the save by his Slovenian colleague to deny Aaron Ramsey's header, which, otherwise, seemed destined for the top corner, was brilliantly kept out with a diving right hand.
The save had a lot of David de Gea about it and we could see why the keeper is drawing such praise-worthy comparisons with the world's best.
His performance on the night proved that he isn't just ready to be compared to the best keepers in the world, but is also ready to compete with them.
Recently, Koke claimed that Atleti should give Oblak a blank cheque to keep him at Madrid. Anyone arguing?
#1 Atletico put themselves in the driver's seat with a crucial away goal after a valiant defensive display
Atletico Madrid will be more than pleased with last night's result in hindsight, considering that they managed to storm the Arsenal ante for almost the entire game with a man short.
Antoine Griezmann and Kevin Gameiro were largely on the periphery of the game and had to put in more of a defensive shift following Šime Vrsaljko's dismissal, with an all hands on deck situation for the visitors.
A couple of opportunities in the game were routinely saved by David Ospina in the Arsenal goal. It's fair to say that the game was more of a training session between attack and defence. And boy, did the visitors give it their all.
their performance on the night epitomised what sets them apart from most teams in Europe. The grit and determination to will themselves on when the task seems insurmountable. And yet somehow, Simeone's men come up with an awe-inspiring display of defensive doggedness which was just as intriguing as their offensive qualities.
Another vintage performance set the stage for them to nick the game on the break and Laurent Koscielny's inability to deal with a hopeless long ball, the ricochet off Ospina and Shkodran Mustafi bundling himself to the ground all amalgamated in a freakish away goal for the Spaniards.
Also read: 3 things that went wrong for Arsenal against Atletico Madrid
We're sure they're not complaining. The Arsenal fans on the other hand
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