The maxim at Arsenal in modern times has been "In Arsène we trust" and if the faith has flagged over the last seven years then it has never been quite so openly challenged as it was yesterday. For all the seasons that have petered out, the famous players that have been sold and the unyielding attitude of the manager in the face of it all, a simple substitution caused the stirrings of an insurrection around Arsène Wenger.
Like all good revolutions, it started with a man from St Petersburg, Andrei Arshavin, who was summoned from the bench on 73 minutes to replace the new darling of the Emirates, Alex Oxlade-Chamberlain. Wenger's team had equalised just two minutes earlier and they looked the side most capable of winning the game with their 18-year-old winger a key presence.
It was not just the malcontents around the press box who rose to their feet and booed Wenger's decision to substitute his winger, it was the expression on the face of Robin van Persie as Oxlade-Chamberlain was summoned to the bench. The Arsenal captain shouted "No!" when he realised what was happening and his response only served to reinforce the disbelief of the supporters who turned on their own manager.
For all of us armchair generals, who do not have the benefit of three Premier League titles to our name and 28 years in management, decisions can be evaluated without the burden of responsibility. Yet, what was striking about the reaction to Wenger's substitution yesterday was the strength of feeling towards him and then the ensuing gloom when subsequently Danny Welbeck scored the goal that inflicted on Arsenal their first run of three Premier League defeats since 2007.
There was even a smattering of ironic applause for Wenger when finally Arsenal were beaten having dominated much of the second half and forced an equaliser through Van Persie with 19 minutes left to play. They had toiled hard to fight their way back into a game in which they were only a marginal presence before the break, when Antonio Valencia's back-post header had put United in control.
It was, sadly for Arsenal, another day when the fissure that has opened between Wenger and some elements of the club's support grew just that little wider. In his press conference, the Arsenal manager was the usual model of glowering defiance. "I have been 30 years in the job. I have made 50,000 substitutions and I don't have to justify every decision to you." He is, of course, right in that respect but that still does not change the reality of the mood in the stadium.
He said that Oxlade-Chamberlain had been "fatigued" and that it was not his responsibility to explain why he was bringing on the captain of Russia for an inexperienced teenager. "Let's be serious," he said, barely able to conceal his contempt. "People pay for their tickets and are free to express their emotions," he said. "We cannot dictate behaviour to people.
"That doesn't mean they're always right. If you expect me to blame an individual player, it will not happen. We win and lose together. You want me to blame one player? I will not do that. If I've made a mistake, I'm sorry. I'm like a player. I'm not completely sure [I will be right]. It could have happened as well if he'd stayed on. That's part of United being dangerous on the flanks."
As for the reaction of Van Persie, Wenger said he had not seen it. He appeared bemused by the questioning as if it had genuinely taken him by surprise. He might have said "I'm sorry" but for the avoidance of doubt he did not sound like a man who felt that way.
The jeers at Oxlade-Chamberlain's substitution gave way to the inevitable calls for Wenger to "spend some f****** money", now the default setting when things go awry at Arsenal. The irony here is that the one player for whom Wenger did outbid all others, including United, was Oxlade-Chamberlain, whose £15m valuation Ferguson balked at when quoted it by Southampton.
The acrimony came later when, with Per Mertesacker as an emergency striker and Arsenal desperately chasing a lead, it became clear Wenger's team had thrown it away. Before then the match never really approached the intensity of the last 35 minutes at the Etihad Stadium earlier. The best moments came when Arsenal attacked the visitors in a strong period after half-time.
In the first half, United had been comfortable with only a Phil Jones injury to concern them when his right knee flexed unnaturally as he retreated in the face of Theo Walcott's run at him. Jones was replaced by Rafael da Silva. Yet it was Arsenal's right-back who suffered more and Johan Djourou eventually came off at half-time, Wenger preferring the 18-year-old Nico Yennaris, a specialist in that position.
Before then, Arsenal had conceded at the end of the half when Ryan Giggs crossed from the left and Valencia met the ball at the back post. United had threatened down that side before then with Nani shooting across goal when he might have been better served squaring the ball to Wayne Rooney.
In the flurry of chances that a rejuvenated Arsenal created at the start of the second half, the best came when Chris Smalling fell over and Tomas Rosicky was able to run at goal. He cut the ball back to Van Persie who made space for himself and then, inexplicably, struck his shot wide. There were further chances for Rosicky and Oxlade-Chamberlain but none as clear cut as that for Van Persie.
Welbeck out-ran Mertesacker and beat Wojciech Szczesny on 65 minutes only for the German defender to scoop the ball off the line. Then finally came the equaliser, a move that began with Laurent Koscielny dispossessing Rafael in the Arsenal area and moving the ball forward to Rosicky. From there it went via Oxlade-Chamberlain to Van Persie who shot through the legs of Jonny Evans and past Anders Lindegaard.
The winner came seven minutes after Wenger's controversial substitution when Arshavin failed to stop Valencia cutting the ball back for Welbeck to score. It was not necessarily the Russian's fault that United scored – anyone might have struggled to stop Valencia – but then it hardly improved the mood, the mood that says Arsenal are struggling once more.
Arsenal: SZCZESNY 6/10; DJOUROU 3; MERTESACKER 5; KOSCIELNY 7; VERMAELEN 7; RAMSEY 6; SONG 6; ROSICKY 6; WALCOTT 4; VAN PERSIE 6; OX-CHAMBERLAIN 7
Man Utd: LINDEGAARD 6; EVRA 7; EVANS 6; SMALLING 6; JONES 6; NANI 7; GIGGS 7; CARRICK 6; VALENCIA 7; WELBECK 7; ROONEY 6
Scorers: Arsenal: Van Persie 71. Man Utd: Valencia 45, Welbeck 81
Substitutes: Arsenal Yennaris 6 (Djourou, h-t), Arshavin (Oxlade-Chamberlain, 74). Man United Rafael 5 (Jones, 17), Scholes (Nani, 75), Park Ji-sung (Rafael, 76).
Booked: Arsenal Koscielny, Rosicky, Ramsey, Song, Van Persie. Man United Evra, Rafael.
Man of the match Oxlade-Chamberlain.
Match rating 7/10.
Possession: Arsenal 50% Man United 50%.
Attempts on target: Arsenal 6 Man United 5.
Referee M Dean (Wirral). Attendance 60,093.