Two Kevin De Bruyne strikes ensured City edged a keenly-contested first 45 minutes, going in 2-1 up - but the champions shifted through the gears in the second-half.
Riyad Mahrez added two more to his tally in the second period, with Pep Guardiola‘s men utterly dominant and perhaps a little disappointed not to have won by an even bigger margin.
What happened?
With most of the talk ahead of kick-off focused on United’s winning run at the Etihad, it felt even more important that City made a positive start.
With less than five minutes on the clock, Kevin De Bruyne provided exactly that.
Jack Grealish and Bernardo Silva combined well on the left of the United box, with the Portuguese then squeezing a low cross into the box where De Bruyne arrived to sweep the ball past David De Gea and score his 50th Premier League goal in the process.
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United came close to levelling just four minutes later when Fred’s quick feet in the box saw him wriggle away from two challenges but Ederson denied him with a fine save.
But on 22 minutes, United caught City on the counter-attack, as Paul Pogba found Jadon Sancho on the left and the former Academy winger, with time and space, cut inside of Kyle Walker, used John Stones as a shield before curling a low shot just inside Ederson’s left post to level the scores.
City responded quickly in what was rapidly becoming a pulsating encounter.
A poor United clearance saw Grealish nod the ball down to Phil Foden who cleverly dinked the ball over Harry Maguire’s head before collecting his own pass and thumping a shot that De Gea saved, then Bernardo saw his follow-up blocked but De Bruyne was on hand to emphatically bury the loose ball home to restore the Blues’ lead.
Sancho had a chance to level before the break but blasted over from 12 yards and Mahrez forced a fine low save from De Gea as an entertaining half ended as it had started.
City began the second-half sharper and more dominant than the first, looking for the third goal that would allow much needed breathing space.
Much of the play was down the left flank, where the impressive Grealish, Bernardo and Foden continually caused mayhem.
All the while, however, United remained a very real threat on the break.
But it was City who scored the crucial ‘next’ goal with a strike straight off the training ground.
Supplied – inevitably – by the gifted right boot of De Bruyne, the Belgian delivered a pinpoint corner to the edge of the United box for Mahrez to half-volley – via a slight deflection off Maguire – past De Gea for his 20th of the campaign.
With 68 minutes gone, there was still work to be done, but the Blues also came close to adding a fourth with a spectacular Joao Cancelo volley that De Gea did well to push out.
However, the coup de grace came on 90 minutes when Ilkay Gundogan won the ball and drove towards the United box before sliding Mahrez through - the Algerian hit a powerful drive into the top right corner despite De Gea’s best efforts.
The offside flag was then raised and it seemed the goal would be ruled out - but VAR correctly spotted the boot of a United defender had played the Algerian onside and the goal - his 21st of the season - stood.
The Etihad erupted accordingly and the goal completed a 4-1 derby win and capped a superb display by the defending champions.
Grealish’s best yet?
From the first minute to the last of this enthralling encounter, Jack Grealish was front and centre.
Always available and willing, he looked confident and assured in almost everything he did.
He was heavily involved in both of City’s first two goals and continually tormented Aaron Wan-Bissaka down the left.
Dropping into pockets of space time and time again, United couldn’t handle his movement and trickery.
It was his best yet in sky blue and a sure sign that he is really starting to find his feet at the Etihad.
What it means...
City go six points clear at the top of the Premier League, though second placed Liverpool have played one game less.
What’s next?
City are back in action on Wednesday evening against Sporting Lisbon at the Etihad in the Champions League Round of 16 second leg tie.
Then, a week on Monday, the Blues take on Crystal Palace at Selhurst Park (20:00 kick-off).
Star man
KEVIN DE BRUYNE
Sensational performance by the skipper who was at the heart of everything good City did on the day.
Two goals and an assist, this was the Belgian at his masterful best.
Pep reaction
To follow...
Line-ups
CITY: Ederson, Walker, Cancelo, Stones, Laporte, Rodrigo, De Bruyne (Gundogan 80), Bernardo, Grealish, Foden, Mahrez
Subs: Carson, Sterling, Jesus, Zinchenko, Fernandinho, Delap. Mbete, McAtee
UNITED: De Gea, Wan-Bissaka, Lindelöf, Maguire, Telles, McTominay, Fred, Sancho, Bruno Fernandes, Pogba (Lingard 64), Elanga (Rashford 64)
Subs: Bailly, Jones, Mata, Dalot, Henderson, Matic, Mejbri
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