Failure on this scale implicates everyone at Manchester City. After that it is just a question of degree. Does most of the blame for this sorry nonperformance and the seeming disintegration of City's Premier League title defence lie with the players, the manager or the owners? Or should they share it equally?
City are 10 points worse off than they were at this stage last season and looking incapable of overhauling Manchester United again even if Sir Alex Ferguson's team suffer another improbable collapse. Indeed, if the dismal manner of their defeat at Southampton is an indication of things to come, even their qualification for the Champions League could be in danger. Rival supporters may scoff that it may not be such a bad thing given how City were embarrassed in that competition this season but for a club of City's ambitions it would be catastrophic.
"If they play like this, they should stay at home," said Roberto Mancini of his team following the St Mary's debacle. The manager has no doubt where the fault lies – unsurprisingly, he says it is not with him.
"When you are a top player you should take responsibility always," Mancini said. "It is not always the fault of the manager, the players should take the responsibility if they have big balls. If not, they can't play in a top team."
There is an obvious retort to that, involving what a manager should do if he has spheres of sufficient size, but first it must be acknowledged that Mancini has a point. How could players not be held liable after Joe Hart gifted Steven Davis a goal by dropping a humdrum shot at his feet and Gareth Barry contributed to Jason Puncheon's strike by tackling him with all the venom of a chocolate soufflé before hurling a pie in his own team's face with the most clownish own goal of the season?
Those were merely the most flagrant symptoms of the mysterious malaise afflicting this team. Too many players have been below par this season. Stalwarts of last season's triumphant campaign have stagnated or regressed. Yaya Touré was billed as the man to lift City against Southampton following his return from the Africa Cup of Nations but instead he served up a sluggish display that reminded us that he has seldom been the fearsome marauder of last term. Ditto for David Silva, Sergio Agüero and Samir Nasri.
Carlos Tevez was absent against Southampton owing to a "personal problem" that Mancini declined to explain but even if the Argentinian had been available he may not have been selected, as the partnership he forged with Agüero after his return from exile last season has only fired sporadically this season.
Edin Dzeko pulled a goal back at St Mary's thanks to a fine counterattack but for most of this campaign City have lacked inspiration, mustering 19 goals fewer in the league than by this stage last season. More alarmingly, at Southampton they seemed to lack motivation, which is unpardonable given that this was identified as a match that had to be won if their title was to be retained.
Mancini accused most of his players of complacency and, again, that looked a fair criticism. But why were they complacent? Mancini has been grumbling all season about a lack of competition for places and on Saturday he again lamented "mistakes made in the summer, when we didn't improve our team". The manager had demanded high-grade recruits such as Robin van Persie and Eden Hazard but was forced to settle for prospects such as Scott Sinclair and Jack Rodwell.
Some players – Nasri and Touré saunter to mind – have looked far too comfortable in the knowledge that there is no adequate alternative to them in the squad. It is also clear that there is no worthy stand-in for the injured Vincent Kompany, nor a midfielder with the rousing leadership qualities of the departed Nigel de Jong.
Mancini blamed the club's then-football administrator Brian Marwood for the underwhelming transfer activity but Marwood was moved aside in October and in January the club again refused to strengthen, confining their activity to restricting Mancini's options even further by selling Mario Balotelli.
The club's transfer policy seems odd or poorly applied. Mancini claims that he enjoys a good relationship with the chairman, Khaldoon al-Mubarak, but it does not appear to be good enough to get what he believes he needs. If there are differences of opinion, the likelihood is that they will either be resolved by next summer or result in divorce.
The outcome could depend on how City fare in the run-in. While Mancini is entitled to complain that the club's recruitment has left him rather constrained, his employers would be entitled to argue that he still should be getting more out of the squad at his disposal. If a player's mindset is wrong, the manager must bear at least some of the blame.
It was hard not to wonder after the performance at Southampton whether the reason the champions were out–fought by Mauricio Pochettino's team was not solely down to complacency but also because one group of players believed fervently in their manager's methods while the other was beset by doubts. There was a disjointedness about City that recalled, for instance, their dishevelled display at Ajax in the Champions League last October, after which Micah Richards said the team was not particularly well versed in the manager's new formation.
At Southampton it again seemed there were square pegs in round holes – the decision to deploy Javier García out of position at centre-back backfired badly and the manager's substitutions did nothing to make City a more cogent proposition. There is also the question of whether some members of the squad have been turned off by Mancini's man-management – his severity with some and perceived indulgence of Balotelli before the striker's departure.
Mancini has lambasted his players but do his players care enough about his view to respond in the way he hopes? "We have a methodology and a philosophy and the players have shown a great willingness and capacity to accept them." That was Pochettino speaking. Who would believe Mancini if he said the same?
Man of match Jason Puncheon (Southampton)