The fanfare had positively blared. Napoli, virtually flawless this season en route to the Emirates Stadium, were to be the acid test of Arsenal's vim and vigour. Rafael Benítez, the manager, has never been any fan of hype but it was nonetheless surprising to hear him attempt to suppress the excitement that has built up around the club. "We probably need to control the euphoria," he said.
This performance did the job. After 16 points from an available 18 had put them second to Roma in Serie A and the home win over Borussia Dortmund on the opening night of this Champions League Group F had further quickened the pulses, nobody saw the big freeze coming. It was jolting, sobering.
Napoli were better in the second half, which might have brought some comfort to the die-hards who packed the visiting enclosure and never stopped bellowing their anthems but they could hardly have been any worse.
The first half was a disaster and it was when Arsenal struck the decisive blows. The home team ought to have led by more.
Everything went wrong for Benítez during those 45 minutes, which ensured that his return to London after his trophy-winning stint at Chelsea last season became an exercise in little more than damage limitation. It was also not a night that did much for the prestige of Serie A. There was anxiety about Napoli, as evidenced by their carelessness with the ball and some heavy touches while Arsenal looked stronger, hungrier and quicker to everything. Play Up Pompeii? Hardly.
The optimism has flowed in Naples after the club's summer transfer dealings, in which the loss of the predator-in-chief, Edinson Cavani, to Paris Saint-Germain for £55m was softened by the impressive attempt that they oversaw to strengthen the collective. But there was a bad omen when the box-office signing, Gonzalo Higuaín, was ruled out with a muscle strain. Higuaín was supposed to join Arsenal in the summer.
Benítez had started with three of his new boys – Pepe Reina, Raúl Albiol and José Callejón – and he had four more among his substitutes. He has sought to implement his own brand of controlled football, with slick passing and explosive counterattacks whilst drumming into new charges the mentality of champions.
But the first half was the stuff of nightmares. Arsenal's confidence overflowed at the outset and Napoli chased shadows; they struggled to get close to them. The Italian team did not get a sniff of the ball until the sixth minute and, shortly afterwards, they fell behind to Mesut Özil's first goal in Arsenal colours.
Italian teams are not supposed to defend like this and nor are uncompromising Uruguayan defenders like Miguel Britos. The centre-half allowed Olivier Giroud to get the better of him on the right flank too easily to release Aaron Ramsey, whose cut-back teed up Özil, although Britos' sloppiness did not explain how his team-mates were drawn towards Reina's line like lemmings to the edge of a cliff.
Britos was also culpable on Arsenal's second. His miscued low clearance from Camilo Zuniga's throw-in was pinged straight at Marek Hamsik and Mathieu Flamini, in close attendance, jabbed the ball to Giroud, who worked a one-two with Özil to punish Napoli. Reina flapped his hands in a funk; Benítez's expression was carved in stone.
Britos had a hapless period and another error almost ushered in Ramsey. He had another wobble early in the second half and only needed a red nose and over-sized shoes to complete the look.
Zuniga, who was inviting trouble with the decision to direct his throw-in from a deep position in-field to Britos, also looked out of his depth.
Arsenal seemed to target the left-back and they swarmed in on his side. Zuniga did, however, have reason to complain about Lorenzo Insigne's defensive work in front of him.
Arsène Wenger had started with five midfielders who would say that they prefer to play in central areas and Napoli's line-up had looked balanced. But any theories were shot to pieces during a first half that Napoli could not wait to end. They had no answers to the rotating Arsenal trio behind Giroud.
Özil was wonderful to watch – his technique is practically indecent - while Ramsey could probably play in goal right now and do no wrong. Insigne's body language towards the end of the first half spoke of the frustration.
Creatively, Napoli offered little, with Insigne shooting wildly over the crossbar and also failing to make a clean connection from closer range. Their only clear chance fell to Britos, who leapt to meet a corner. This was not going to be a night where he found the top corner.
Napoli had to be better in the second half; their pride demanded it and they were, even though their success was measured more in the way that they slowed down the Arsenal juggernaut. There was more wild shooting from Insigne and it was difficult to remember anything from the centre-forward Goran Pandev prior to his substitution, although he was far from the only disappointment. Reina saved at point-blank range from Laurent Koscielny as Arsenal were denied the gloss that they deserved. Napoli will want to forget and refocus.