Five days is an awfully long time in football. On Tuesday night, Arsenal slumped to a 3-2 defeat to Olympiacos, leaving their Uefa Champions League chances on a knife-edge after just two group stage matches.
The response against Manchester United on Sunday afternoon, though, was as emphatic as that loss had been disappointing.
Before Roman Abramovich and Jose Mourinho arrived at Chelsea and broke Arsenal and United's duopoly just over a decade ago, this was always the biggest and most important fixture in the Premier League.
It has lost some of its significance in the years since – Arsene Wenger's side have not won the title since 2004 – but Arsenal produced the type of scintillating performance that suggests they are genuine contenders for the crown this term.
The hosts began the game in the ideal manner: fast, intense and strong in the challenge. They circulated the ball at speed, disrupting United's shape and forcing the visitors to give chase from the first whistle.
It did not take long for Arsenal to be rewarded for their positive, proactive approach. Alexis Sanchez opened the scoring with a fancy flick after great work from Mesut Ozil, with the German adding a second soon after to give Arsenal a 2-0 lead in the opening seven minutes.
There was no time for United to rest and regroup, with the Arsenal onslaught showing few signs of abating.
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Sanchez added a third before the halfway point of the first period, smashing an unstoppable shot into the top corner of the net to send the home crowd into delirium.
They played some sparkling attacking football throughout the first 45 minutes.
It was also noticeable that Arsenal were far hungrier than United, quicker to every loose ball and triumphant in almost every physical battle across the pitch. The space United afforded Arsenal between the lines was extraordinary.
In trying to push onto Santi Cazorla and Francis Coquelin, Bastian Schweinsteiger frequently got caught too high up the pitch, leaving his side exposed to runners breaking beyond him.
The Germany international just does not have the legs to perform such a function anymore; with Ozil, Sanchez and Cazorla causing havoc in the sizeable pockets between the United midfield and defence, it became increasingly curious that Morgan Schneiderlin, the most energetic holder in the United squad, had been left on the bench.
Arsenal showed another side to their game after the interval, demonstrating a pragmatism and ability to manage a match that they have rightly been accused of lacking in the past.
Wenger shifted to a 4-5-1, Ozil moving out to the right and Aaron Ramsey becoming an extra body alongside Coquelin and Cazorla in the centre.
Arsenal succeeded in shutting the game down and, while United enjoyed a large share of possession, they were toothless in attack and missing craft and creativity in behind.
Wenger has frequently been labelled too much of an idealist, someone unwilling to adapt his tactics to negate the strengths of the opposition.
It was Louis Van Gaal who was guilty of such oversight on Sunday, however.
United attempted to impose themselves on Arsenal too early on, pressing high up the pitch and leaving huge gaps that a technically excellent side took full advantage of.
Despite United's faults, though, the afternoon belonged to Arsenal, who, after Tuesday night's ineptness, offered the perfect riposte to those who have suggested they do not possess the requisite mental strength to finish top of the pile after a gruelling campaign.
It was always going to be imperative that Wenger's men reacted to the adversity of midweek with a victory against a side who many expect to challenge for the title this season, but it will have been especially pleasing for the Frenchman that they did so in the most convincing and comprehensive fashion possible.
The key now is to avoid having to bounce back from such situations in the first place.
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