As shock defeats come, newly-promoted, injury-ravaged Norwich City taking down all-conquering defending champions Manchester City is right up there as one of the most surprising in Premier League history.
That loss underpinned an entertaining Premier League weekend which also saw Arsenal drop points for the third straight game while Tottenham and Chelsea got back on track with thumping wins.
But how and why did it all happen? Goal breaks down the major tactical lessons from the key fixtures...
1) Farke's two-part plan undoes Man City
It was an unbelievable performance, an act of collective heroism that will never be forgotten by the home fans inside Carrow Road.
But Norwich's win over Man City was not just about digging deep or playing with bravery; it was a tactical victory for Daniel Farke that can be split into two distinct parts.
Off the ball, Norwich sat in a surprisingly deep and narrow 4-2-3-1, which is markedly different from their open formation in previous games this season - and varies from a flat 4-5-1 that most teams would naturally drop into when falling back.
Keeping a tight W-shape in midfield meant their narrow wingers cut off the passing lines to David Silva and Ilkay Gundogan while No.10 Marco Stiepermann closed down Rodri and stopped him picking creative passes.
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The hosts’ shape deliberately left the Man City back four free to pass harmlessly, only to snap into the press in short bursts when the ball was shuttled wide into the full-backs where, with a touchline so close, they can be surrounded.
The second part of their plan was to pass out calmly under pressure, immediately reverting to Farke’s one-touch passing triangles even when Man City tried to counter-press.
This prevented Norwich from getting penned in, and gradually meant the visitors were forced to sit off – a meeker tactical approach that Guardiola’s team are uncomfortable attempting. Norwich never looked like being caught, such is the brilliance of their fluid football, and splitting duties – six stay back, four go forward – certainly helped.
2) Guardiola gets it wrong with emphasis on width
To beat Man City you need to be perfect, lucky, and catch Pep Guardiola’s team on a bad day.
For the latter, blame the manager’s strange emphasis on width despite Norwich regularly conceding goals and high quality chances in recent matches via the central column.
Raheem Sterling and Bernardo Silva were too wide from the off and were not supported by overlapping runs, meaning they were constantly left trying to beat a full-back from a standing start – only to see their hopeful cross comfortably cleared away.
Ordinarily their width is an asset because Kevin De Bruyne comes short to dictate the tempo, cutting the midfield open and releasing the wingers into space, but in his absence Gundogan and David Silva held too high starting positions.
Man City looked at their most threatening on the rare occasions when Sterling drifted into the half-space and drove at the Norwich defence, and yet Guardiola’s second-half substitutions doubled down on attacking the flanks.
Gabriel Jesus joined Sergio Aguero in the box as De Bruyne was evidently instructed to move out to the right and whip balls in; Man City attempted an extraordinary 47 crosses, more than twice their season average.
PIC: Man City crosses vs Norwich
Norwich could have been panicked had Man City bunched centrally and passed their way intricately into the final third, but with new partnerships in midfield – and their two best players hugging the touchline – Norwich held firm.
3) Emery's dodgy diamond fails again for Arsenal
The logic behind Unai Emery’s diamond 4-4-2 was sound; Watford usually deploy a narrow 4-2-2-2 and so Arsenal needed numbers in the middle, plus Quique Sanches Flores’ defensive instincts meant Mesut Ozil and Dani Ceballos may have been required to thread through a compact defence.
However, it quickly became apparent that Watford were braver than anticipated and willing to constantly hit the flanks – and yet Emery did not change his formation until it was too late.
Gerard Deulofeu had a remarkable 92 touches of the ball, his energy - supported by Jose Holebas - making a mockery of Emery’s decision not to give makeshift right-back Ainsley Maitland-Niles support from a winger.
In a diamond shape Arsenal simply did not have any bodies to cover the full-backs, which explains why Watford were able to attack so successfully down the left time and again.
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That Watford could get the ball out wide so easily was hardly a surprise to anyone who regularly watches Arsenal in away matches. Their midfield was typically aimless and non-confrontational, stepping right off in a clueless manner.
Granit Xhaka was perpetually drifting from his position at the base of midfield; Ceballos understandably had no idea how to play centre-left midfield.
Arsenal eventually switched to a 4-2-3-1 but could not stem the tide, particularly once Flores strengthened the right flank by introducing Daryl Janmaat to drive at Arsenal’s equally under-stocked left. His run helped earn the equalising penalty, and the Dutchman very nearly created a late winner.
4) Lampard channels his inner-Conte to stabilise Chelsea
Throughout the season Chelsea have struggled to close off gaps in central midfield, and though Wolves’ two second-half goals show this remains a big problem, Frank Lampard’s switch to a 3-4-2-1 did help stabilise the visitors.
The formation was picked only to negate Wolves’ three-man defensive structure, but after this display Lampard may consider keeping his new system.
Deploying a third centre-back meant one of them – mostly Fikayo Tamori - could step out to meet any attackers who outmanoeuvred that troublingly naïve central midfield. The 21-year-old also stepped out when Chelsea had possession, helping to break the lines and assist in the quick, vertical build-ups Lampard preaches.
More importantly, the 3-4-2-1 meant Mason Mount and Willian played in narrow Antonio Conte-esque inside forward positions, creating a box-shape four in midfield that gave Chelsea a numerical advantage against Wolves’ three.
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Both players dropped into intelligent positions to receive passes from Jorginho and gallop at the Wolves back line, pinning the hosts back in a rampant first-half display.
Given that clumsy full-backs Cesar Azpilicueta and Marcos Alonso benefited from an extra defender behind them, perhaps Chelsea should stick with a 3-4-2-1.
5) Spurs regain their spark in Palace pummelling
Usually so dull and unimaginative against bottom-half teams in 2019, Tottenham finally ended a worrying trend by playing assertively on Saturday afternoon against Crystal Palace.
The passing was sharp, the movement direct, and the mood confident – with Toby Alderweireld, Serge Aurier, and Son Heung-min the most important players.
Spurs under Mauricio Pochettino have traditionally broken down deep-lying opponents with quick, powerful full-backs providing width, and Aurier’s performance was a reminder why they should not play Juan Foyth in games like these.
His two assists were down to brute force and speed of thought, exactly what was needed to raise energy levels inside the Tottenham Hotspur Stadium.
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It was Alderweireld, however, who set the tempo with excellent searching long balls over the top of the defence. Palace were frantically backpedalling from the off, giving Spurs the impetus to keep releasing a hungry-looking Son.
Spurs are bad at recovering from slow starts; here was a reminder of why they need to be all-guns-blazing from kick-off.