A season that promised so much and delivered on many fronts for Manchester City fans will now slide gently to a rather subdued conclusion.

City's failures in the past seven days will be scrutinised and picked over for some time. Three defeats in that short space of time feel like a real hammer blow to a club that had danced through the minefield of a tough 2017-18 season like they had wings attached to their boots.

So, what went wrong?

Firstly, runaway success brings its own perils. Strange as it may seem, being so far out in front for so long can produce a state of mind and an atmosphere that can become counter-productive if it is not managed properly. Expectation goes through the roof. Every little setback appears to be the end of the world.

City's lead in the Premier League has gradually been extended over a long period to the point where, still not champions, everyone has been treating them as such for weeks. The players' capacity to remain focused and to play at full steam can only be compromised by this.

Some will save their legs for the big games coming, while others will go through the motions, thinking the job is done. Obviously, with a manager as thorough as Pep Guardiola bestriding the touchline, anyone erring will soon hear about it. Still, it is difficult to imagine some not performing slightly below their best.

Anyone watching City's season as a whole will vouch for the fact that most of the very best performances came before Christmas. The last four games have offered a snapshot of this with a scintillating first half at Everton followed by a training-exercise second half. Brilliant first halves against Liverpool and Manchester United also gave way to something less palatable after the break.

Guardiola himself is another factor. His intensity leaves the possibility that some of his groundbreaking tactical tinkering may backfire. The away game at Liverpool in the Champions League was arguably not the moment to change the team's shape and to usher in alternative personnel.

True, Raheem Sterling had been psychologically compromised by the baying crowd in City's 4-3 league defeat at Anfield, but it felt like Liverpool were gaining an advantage because City were changing format just for them. Psychologically, that can work in different ways on both teams.

Guardiola's early departure from the touchline in the second leg also had an effect on his team. With the Catalan twitching and twisting high in the executive seats after referee Antonio Lahoz had shown him the red card, City's players had no tactical inspiration from the sideline. A motionless Mikel Arteta on the bench came in stark contrast to Guardiola's constant pacing and cajoling routines.

City's form has faded just at the wrong time. Matthew Ashton - AMA/Getty Images

In addition, the role played by referees this season cannot be ignored. City have been short-changed in this department all season. You probably have to go back to Don Revie's Leeds side of the early 1970s to find a top team that has been so badly served by officialdom in the English game.

Aside from Lahoz's error in failing to overrule his linesman against Liverpool when Leroy Sane scored a perfectly legal second goal, the away game also featured poor decision-making by the referee, as did the Manchester derby sandwiched in between. Missing what looked like a deliberate hand ball by Ashley Young, Martin Atkinson compounded the error by waving play on when the same player demolished Sergio Aguero's leg in the penalty area.

It is fair to say that City were deservedly beaten by Liverpool over the two legs -- a weak first leg was particularly damaging -- but who is to say what kind of thrust a second goal would have given Guardiola's side just before half-time? Liverpool were coping with City's onslaught as capably as City had done with Liverpool's a week earlier and would likely have wobbled some more had they gone in at half time two-down.

A rash of unpunished fouls on City players before Christmas must not be forgotten either. Not only were there five or six clearly dangerous fouls committed that went without red cards, the resultant injuries also affected City's progress adversely.

It was shortly after one of these assaults that Kevin De Bruyne, the main target of the persistent fouling, stated that he was beginning to feel tired.

De Bruyne, touted for so long as a possible European Player of the Year, has mirrored City's season with his own performances. The Belgian's form has dipped below the miraculous output of the first four months. Those raking through balls and astonishing curling shots have begun to dwindle just at the wrong moment. The fresh impudence of the free kick he rolled under the leaping Cardiff wall in the FA Cup has been replaced by a hunch-shouldered slog towards the finishing line.

It is at times like this difficult to avoid thinking of this as a metaphor for the entire Manchester City season.