Manchester City's 1-0 loss to Tottenham in February felt at the time like a game which may come to define their season.
Only a fortnight earlier, Pep Guardiola's side had fought back from two goals down to seal a stunning 4-2 win over the same side at the Etihad Stadium. To then lose to them, a day after Arsenal had dropped points against Everton, summed up their inconsistency.
The setback followed defeats against Manchester United and Brentford either side of the World Cup and ensured that they had lost as many times in eight Premier League games as they had in the whole of the previous campaign. They were not themselves.
Or at least, that's how it felt. It has all changed now. Since that defeat to Spurs, City are unbeaten in 16 games. The treble is on. Arsenal have been hunted down to such an extent that, given their games in hand, a City win at the Etihad on Wednesday night could effectively seal the Premier League title with a month to spare.
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City feel Dias effect
There are many factors behind City's rejuvenation and the return of Ruben Dias, following a hamstring injury sustained with Portugal at the World Cup, is undoubtedly a significant one.
Guardiola was cautious when reintroducing him following his month-long absence, naming him on the bench in four consecutive games - only one of which he appeared in at all - before putting him back in the starting line-up against Aston Villa on February 12.
Even then, he continued to tread carefully. Dias impressed in the first half against Unai Emery's side as City roared into a three-goal lead but he did not emerge for the second period, Guardiola later citing his booking for dissent as the reason for his withdrawal at the interval. "Of course he was disappointed," he added.
That disappointment did not seem to linger.
And if it did, then it has served as motivation.
Dias was outstanding in the subsequent 3-1 win over Arsenal at the Emirates Satdium and has been practically ever-present since, starting 15 consecutive games in all competitions - the longest-run by any current City player this season - before he was rested for Saturday's FA Cup semi-final win over Sheffield United.
City won 12 of those 15 games, taking 25 points from a possible 27 in the Premier League, and the extent of his influence becomes even clearer when looking at the season as a whole.
In the 30 games Dias has started in all competitions either side of the World Cup, City have a win rate of 77 per cent compared 63 per cent without him. Take out the Community Shield and they have actually only lost once with him in the side all season.
Their defensive record is far better when he plays - City have only conceded nine times since his return from injury - and his importance stretches beyond his physical and technical qualities.
The 25-year-old, although third in the captaincy order behind Ilkay Gundogan and Kevin de Bruyne, is City's true leader, a player, as Guardiola explains, with the rare power to lift those around him.
"Ruben is not playing just his game, he is playing the game for everyone," explained the City manager in March. "He has the ability to see and solve the problems for many things. His character is so important, and his leadership is huge."
Cancelo's exit, Pep's shapeshifting
Dias' return to the team followed the unexpected exit of his countryman Joao Cancelo, who was abruptly sent on loan to Bayern Munich at the end of the January transfer window.
It was an extraordinary gamble by Guardiola - especially as there was no time to bring in a replacement. Cancelo had become one of his most important players, featuring in the PFA Premier League team of the year for the last two years running, then starting the first 18 consecutive games of the new campaign.
Later, though, when Cancelo lost his starting berth, Guardiola resolved that his personality was not suited to a supporting role, and that it was better for everyone if he was moved on.
If it was intended, on some level, as a message to the rest of the squad about the commitment and dedication he demands, and a reminder that nobody, not even his most valuable and experienced players, is exempt from meeting those standards, then it certainly resonated.
At one time or another in the last three months, Guardiola has elicited crucial contributions from nearly every member of his first-team squad, including those not playing regularly.
But it was not just a means of galvanising the group in a time of need. It was also about doing something different with the team. Guardiola's brilliance lies in the fact that he is forever evolving. Cancelo was just the latest casualty.
Without him, Guardiola implemented a dramatic change of shape, his defence effectively adjusted from a four to a three.
The formation is fluid and involves numerous variations but it has given City an air of unpredictability at a crucial point in the season. They have now started with three at the back in five of their last seven Premier League games and won them all.
Those players required to adapt following Cancelo's departure have delivered. Nathan Ake, someone who, in contrast to Cancelo, has been praised by Guardiola for his atitude during his spells on the periphery, has excelled as a left-back in games when City have reverted to a four.
Even Bernardo Silva has stepped into that role willingly at times and there have been adjustments on the other side of the pitch, too, with John Stones used as a right-sided defensive midfielder in games against Crystal Palace, Liverpool and Southampton.
It is a testament to Guardiola's coaching ability that players such as Stones have been able to excel in such alien roles and the result of their changing shape is a City side that is more defensively secure and even more dominant, its opponents struggling to keep up.
Getting even more from Haaland
It is not just City's defensive players who have stepped up.
Erling Haaland has set such ludicrously high standards that a run of four goals in 11 games between January and February felt like a drought, but his output has exploded since.
This can be seen when looking at his rolling average for goals and expected goals in the Premier League over the course of the campaign. Having previously been in decline - albeit from extraordinary heights - his numbers are now back on the ascent.
Factor in all competitions and the Norwegian has smashed 16 goals in his last 10 games, during which time he has equalled Mohamed Salah's record of 32 in a 38-game Premier League season.
It is partly a consequence of his relationships with team-mates continuing to strengthen the more he plays with them, but the change of system has helped too. With a defender sacrificed for an extra midfielder, Haaland is getting more support and is less isolated. City's overall attacking threat has increased.
And while he has had a seemingly telepathic understanding with Kevin de Bruyne since the very start of the season, he is now combining similarly effectively with wingers Jack Grealish, who has been outstanding since the World Cup, and Riyad Mahrez.
Depth and rotation paying off
City are also feeling the benefits of Guardiola's rotation policy, something which contrasts starkly with the approach of their title rivals Arsenal under Mikel Arteta this season.
Indeed, while City have made 71 changes to their starting line-up in the Premier League, the fifth-highest total in the division and an average of 2.4 per game, Arsenal have made only 30, the lowest total in the Premier League and an average of only 0.9 per game.
Arsenal have of course had a clearer schedule following their early exits from the domestic cups and last-16 defeat to Sporting Lisbon in the Europa League, but it is little wonder they are showing signs of fatigue at a time when City are picking up the pace.
Guardiola voiced fears of "exhaustion" after the two-legged Champions League victory over Bayern Munich but, as ever, he has handled his players' loads delicately and deliberately in order that they have enough stamina in reserve for this point of the season.
City have played two fewer games than Arsenal but it is worth noting that only one of their outfield players - Rodri - has played more than 2,400 minutes in the Premier League this season while Arsenal have six already well past that milestone.
City's resources are crucial in this regard. Arteta feels he cannot do without certain players in his starting line-up but City's depth of quality is such that, in almost all areas of his team, Guardiola can make changes without feeling the level will dip.
As such, when the home straight comes into view, he is able to ensure that City still have enough in the tank to get over the line. That is certainly how things appear to be shaping up this season.
Experience and psychological edge
It is of course a question of psychology too.
City are serial winners who have been here before and it is inevitably in the latter months of the season that their capacity to withstand the kind of pressure others can't really begins to show.
Last season, they were similarly relentless, going unbeaten in their last 12 Premier League games on their way to pipping Liverpool to the title. The year before that, the crown was effectively secured by a run of 15 consecutive wins between December and March. The 2018/19 campaign saw something similarly spectacular.
It helps, too, that so many of their players are accustomed to winning trophies.
Between them, the Manchester City squad have won 179 pieces of silverware over the course of their top-level international and club careers. Arsenal, by contrast, do not get close to that number, with only eight Premier League titles to City's 51.
City would of course rather have approached the second half of the season on top of the table with a cushion on their nearest rivals, but there is also something to be said for being the one chasing rather than the one setting the pace.
Liverpool might disagree after the events of last year, when they fell just short of the title after a season on City's tail in the Premier League, but it is psychologically preferable to be hunting down a target rather than looking over your shoulder.
That is certainly how City have made it look lately, but it is just one of many factors. Only two months ago, it seemed their Premier League title defence might be doomed to end in disappointment. What has followed is a lesson in not writing them off.
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