Arsenal are never as vulnerable as when they’re optimistic. Three wins in a row and no goals conceded, added to Tottenham’s recent woes, had nudged the Arsene Wenger crisis-o-meter away from “must go” towards “may have another campaign in him” but whatever hope may have been beginning to kindle within the Emirates were brutally stamped out within 11 minutes. What makes it worse is that it was all so familiar as Arsenal’s Jonah Complex struck again.

It’s a condition outlined by the US psychologist Abraham Maslow, who is most famous for his hierarchy of needs. Jonah in the Old Testament is instructed by God to go to the Assyrian city of Nineveh to prophesy the destruction of the city for its wickedness. Terrified by the prospect, he instead flees in the opposite direction and takes a ship. He is thrown overboard and swallowed by a whale.

Maslow saw talent as a responsibility akin to that faced by Jonah. For him, the greatest achievements carry an element of risk: they are a trial of ability and temperament. To strive for achievement is exhausting, mentally and/or physically. It is a process with the potential for significant cost. How much more comforting, then, to embrace self-destructiveness, to commit acts of self-sabotage, to diminish the consequences of coming up short. “Ah, but if it hadn’t been for those two early mistakes…”

But the point is Arsenal did make those early mistakes and that dictated everything that followed – and Jose Mourinho was waiting for them. There is a passage in Diego Torres’s controversial biography of Mourinho, written when he was at Real Madrid, in which he sets out the Mourinho plan for away games. Essentially it’s a programme for negative football: keep it tight, take no risks, wait for mistakes to happen. “He who has the ball has fear,” runs the most chilling line.

It hadn’t previously worked for Mourinho at United – his previous six away games against members of the big six had yielded only one goal, Wayne Rooney’s consolation in defeat at White Hart Lane last season – but he hadn’t previous faced an Arsenal side that had begun to believe in itself.

Wenger, anyway, is Mourinho’s bunny. Thirteen previous league meetings between the managers had brought a solitary win for Wenger, and that towards the end of last season after Mourinho had effectively given up on the league to focus on the Europa League. But still, the capitulation was shocking. After the intensity that had worn down.

Laurent Koscielny had a error-strewn game (Getty Images)

Tottenham two weeks ago, there was an astonishing laxity in those opening minutes – perhaps a complacency induced by that easing of pressure, perhaps just non-specific sloppiness. Laurent Koscielny gave the ball away to initiate the move that brought the first. The French defender bore some responsibility for the second as well, as his pass onto Shkodran Mustafi’s weaker side led to the German being caught in possession by Jesse Lingard in the build-up to the second.

Perhaps Mourinho had never intended to sit deep. Perhaps he was planning to go for the jugular. We’ll never know: ruthlessly brilliant as United were in seizing the opportunities gifted them, they were gifts, and they changed utterly the dynamic of the game. Arsenal played extraordinarily well after that and but for a string of outrageous saves from David De Gea would have own the game, which Wenger will probably portray as evidence of their strength of character, but this is a recurring theme.

Again and again in the past decade, Arsenal have battled back not quite well enough after early, often self-inflicted, setbacks, as though they feel the need to make the mountain larger before they start climbing it. That is characteristic of the Arsenal psyche, as though they as a club must always make the possibility of success impossible before they begin playing for real.

Given the harum-scarum nature of what followed, it would be easy to be seduced by that narrative, but the point is those two goals did happen, just as Arsenal have undermined themselves in recent seasons against Bayern, PSG, Monaco and AC Milan. It’s somehow become part of their nature, particularly when things seem to be going well. And had it not been for those two early goals, Arsenal would not have been so committed as to be caught on the break either for the third, or for the Lingard effort that Cech had turned onto the post 14 minutes earlier.