London - Whether it was the weakness dealing with low shots to his left or the chest-beating patriotism prior to England's Euro 2016 fixtures, something happened in France this summer to convince Pep Guardiola that Joe Hart could not be relied upon as his first-choice goalkeeper at Manchester City.
The new City manager's concern over Hart's distribution of the ball with his feet was already a flaw that the Catalan had identified as something which required work, but the die had not been cast for the England number one when Guardiola was confirmed as Manuel Pellegrini's successor last February.
Guardiola believed that Hart's footwork could be improved - he insisted 24 hours prior to the season opener against Sunderland that he had seen signs of the 29-year-old's ability to grasp the nettle - but when push came to shove on the opening weekend, it was Willy Caballero who stood in goal for City, with a brooding Hart forced to watch from the bench.
Hart has at least been reassured by England manager Sam Allardyce that he will retain a place in the squad for the World Cup qualifier against Slovakia on September 4, but at City, he is now reduced to hoping for a run-out in the second-leg of a Champions League Play-Off against Steaua Bucharest on Wednesday in a game, with City leading 5-0 from the first-leg, which has become the absolute definition of a dead-rubber.
It has been a brutal fall from grace for a player who has earned his place in City's hall of fame, with two Premier League winners' medals and success in both domestic cups.
There have also been some breathtaking performances in the Champions League, against the likes of Barcelona and Borussia Dortmund, when Hart has saved his team from humiliation with, at times, superhuman displays of resistance.
But those career-defining nights against Lionel Messi and Robert Lewandowski have perhaps masked Hart's stagnation as a goalkeeper in recent years.
Goalkeeping great Peter Shilton, who remains England's most capped player, left no room for doubt with his evaluation of Hart following his erratic performances at Euro 2016.
“I've always said I don't think Joe is as good as a lot of people think he is,”Shilton said. “He's a good keeper, but he's prone to making errors, and not just for England.
" There's competition now and in my eyes he's not an automatic choice at the start of this season.”
Shilton has been proved right, both with City and England, but alarm bells began to ring loudly for Guardiola during the summer, when Hart was beaten easily by Gareth Bale and Kolbeinn Sigthorsson, against Wales and Iceland respectively, with low shots to his left.
With every angle now covered on a players' strengths and weaknesses, Hart's fallibility at the left-hand post, and down low to shots on the left side, are an open secret, but the problem appears to be getting worse rather than better.
Has Hart spent enough time working on those weaknesses? The recurring fault suggests that he has not or, perhaps even worse, he has worked on it but simply been unable to correct the flaw.
So with a long-term fault showing no sign of improvement, how could Guardiola spend time waiting for Hart to become comfortable and reliable when receiving and distributing the ball with his feet, as Victor Valdes and Manuel Neuer did so impressively for the coach at Barcelona and Bayern Munich? Technical weaknesses can be rectified with practice and repetition, but maybe the bigger issue for Guardiola is Hart's tendency to allow himself to be overtaken by a sense of occasion.
Hart was embarrassed by Andrea Pirlo's 'Panenka' penalty during the shoot-out defeat to Italy at Euro 2012, when the midfielder dismissively scored from the spot following the 'keepers' attempts to distract him with facial gestures.
But with Hart whipping himself into a frenzy before England's Euro 2016 games -loudly shouting and gesticulating in the tunnel before beating his chest in front of the supporters -it brought to mind a passage from Rio Ferdinand's autobiography, #2SIDES, which explained the secret to Manchester United's success when faced with a big game.
“The approach was always: calm, cool, relaxed, focused, clear-headed,” Ferdinand wrote. “Always prepare the same way.
“Don't get involved with nerves or extra shouting. Never get carried away by hype of emotion.
“Never think: 'we've got to win this match to win the league.' Just go out, get your three points, be normal.' Hart was anything but normal in France, but he certainly allowed himself to get carried away with hype and emotion.
So on the pitch, he gave Guardiola reason to doubt his qualities and off it, he suggested to his new boss that his personality could change, for the worse, when dealing with a big occasion.
The axe may have fallen swiftly and unexpectedly on Hart at City, but in reality, it has been coming and the signposts have been erected by the man himself.
At 29, there can be a route back and Hart is good enough to find it, but it will not be at Manchester City.
The Independent