For Manchester City it was a supreme way to round off an immaculate week. One by one they have been ticked off: first Arsenal, then Everton and finally a Chelsea side that looked in need of smelling salts before the midway stage of the first half. Three games, 11 goals, nine points, and more fool anyone who thought this might be the most difficult assignment of the lot.

What actually happened was a peacock-like spreading of City’s feathers, featuring a four-goal blitz inside the opening 25 minutes, another hat-trick for Sergio Agüero and the feeling, once again, that, if Liverpool can beat this team to the Premier League title, it will rank as the most exceptional performance of any of the championship-winning sides from Anfield through the years.

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If anything it was just a surprise City did not add even more sheen to the margin of victory bearing in mind there was never a single part of the match when they looked bored by their own brilliance. City, to put it into context, have now scored twice or more in every Premier League home match this season, a feat no top-division team has managed in 15 successive games since Tottenham Hotspur from March to December 1965, with Bill Nicholson in the dugout and Jimmy Greaves terrorising opposition defences. Including the cup competitions the reigning champions have accumulated 33 goals from their last six home games. It feels like a statistic from another time, a sepia-tinted era of baggy shorts and boggy pitches.

For Agüero it was his 15th hat-trick in City’s colours and perhaps it would be impertinent to dwell too long on the moment, at 1-0, when he also produced possibly the worst miss of all his years in English football. Two yards out, Agüero might argue one would have to go back in time even further to find similar. No matter: his first goal came five minutes later and perhaps there was a measure of anger contained in his firecracker of a shot, 25 yards out, into the top corner of Kepa Arrizabalaga’s net. Missing a sitter, scoring a screamer – who cares if it was unorthodox when Agüero has 25 goals in his last 16 starts for City at this ground?

By the time Pep Guardiola’s team were done they had moved back above Liverpool to the top of the table, albeit having played a game more, and it did not seem unreasonable to wonder whether this result might seriously endanger Maurizio’s Sarri’s position as Chelsea manager. Put it this way: Roman Abramovich has sacked good men for considerably less.

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This was their fourth successive away defeat in all competitions and everyone connected with Chelsea, not just Abramovich, must be alarmed by their deterioration, particularly having just been whacked 4-0 at Bournemouth. The final goal means Chelsea drop below Arsenal to sixth place on goals scored. Yes, there is the Carabao Cup final to come on 24 February and a chance to decorate an increasingly problematic season with some silverware. Just do not bet your mortgage on it: the opposition at Wembley will be … Manchester City. Maybe Guardiola will start David Silva next time, too.

Chelsea have not managed an away goal since 30 December but their problems here owed more to chaotic defending and a collective meltdown after it all began, four minutes in, with Kevin De Bruyne slipping a free-kick behind the opposition defence to find Bernardo Silva completely free. Silva jinked into the penalty area and his low cross flicked off David Luiz to roll invitingly into Raheem Sterling’s path. Sterling found a gap between Arrizabalaga and the goalkeeper’s right-hand post and, after that, it was startling to see Chelsea’s capitulation.

Play Video 1:04 'I'm always at risk' of being sacked by Chelsea, says Sarri after humiliation at Man City – video

If nothing else, at least there were some encouraging signs for Sarri that Gonzalo Higuaín can flourish as the new arrowhead to Chelsea’s attack. No team, however, can expect to get away with defending as abjectly as Chelsea did during the period in the first half when most of the damage was inflicted. Chelsea conceded a goal on average every five minutes and, though an argument could be made that City pressured them into mistakes, that was not always the case.

Agüero’s second goal was a case in point, originating from Ross Barkley trying to head the ball to his goalkeeper from the edge of the penalty area. It is an old Paul Gascoigne trick and, if it comes off, with so many opponents in close proximity, it looks good. If it does not, it can make the player who tried it look foolish in the extreme. Barkley got it horribly wrong and Agüero pounced to get in front of Arrizabalaga and score with a swivelling left-footed shot.

Quick guide Premier League title race: the remaining fixtures Show Hide Manchester City (86 points) 24 Apr Man Utd (a)

28 Apr Burnley (a)

4 May Leicester (h)

12 May Brighton (a) Liverpool (85 points) 21 Apr Cardiff (a)

26 Apr Huddersfield (h)

5 May Newcastle (a)

12 May Wolves (h)

If Chelsea had been fully prepared, they should not have been taken aback by the early onslaught. City have now scored 15 times in the opening 15-minute periods of their league matches this season and the next most impressive figure belongs to Arsenal, with seven. It was 3-0 after 19 minutes and Ilkay Gündogan, a player who deserves far more acclaim than he actually receives, swiftly made it four, catching out Arrizabalaga with a 20-yard effort into the bottom corner.

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Agüero completed his hat-trick from the penalty spot 11 minutes into the second half, after César Azpilicueta’s foul on the elusive and merciless Sterling, and City’s record scorer also headed one of De Bruyne’s beautifully delivered crosses against the crossbar before making way for Gabriel Jesus.

Oleksandr Zinchenko, drafted into City’s defence and outstanding throughout, supplied the cross for Sterling to finish the scoring. It was the heaviest defeat Chelsea have suffered in the Abramovich era – the heaviest, indeed, since losing 7-0 at Nottingham Forest in 1991, back in the days of Gordon Durie, Kerry Dixon and Tony Dorigo – and, when Sarri went straight down the tunnel at the end without shaking Guardiola’s hand, perhaps, to give him the benefit of the doubt, it was not a deliberate snub on the part of Chelsea’s manager. His mind might have been filled by thoughts of what this defeat means for his job prospects.