“Mind the gap”; “Old Trafford is falling down”; and “we’ve got Guardiola”: what a day for Manchester City fans, who delighted in these choruses as their team swatted aside a Manchester United side that was devoid of ideas.

Erik ten Hag’s side failed miserably to give Sir Bobby Charlton what the great man would have craved: a victory. Or, even, a performance because they lacked any consistent creative plan and faced an opponent who possesses one.

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For a while in the first half this derby had a throwback feel as United and City scuffled for ascendancy. Then, the champions turned the screw and blew away a United who ended seriously embarrassed. When Phil Foden tapped Erling Haaland’s unselfish ball over André Onana’s line it had swathes of home fans departing, and the manner of the strike summed up the state of their team. This City third was presaged by Rodri being allowed by an uninterested Christian Eriksen to pad forward and shoot – when Onana saved there was the Norwegian to set up Foden.

Haaland began with nine Premier League goals and ended with 11. The 10th came before the break and from the spot: a hapless Rasmus Højlund yanked down Rodri and the 6ft 4in striker sent Onana the wrong way. His second came after the change of ends – from a dipping Bernardo Silva cross, as the United rearguard was sucked right to leave Haaland unmarked to finish.

The blame for United’s disarray has to lay with Ten Hag, who after 17 months and three transfer windows has constructed a side with scant apparent gameplan and too many low-grade players.

The defence the manager sent out here acts as an emblem of his thinking. When United fans read the names of Victor Lindelöf, Harry Maguire, Jonny Evans and Diogo Dalot any hope they harboured surely faded – especially as Ten Hag declared that Raphaël Varane was out for a “tactical” reason.

This baffled given that Lindelöf, Maguire and Evans are second-choice defenders and Evans is 35. Haaland’s second goal illuminated the manager’s folly because Lindelöf, his nominated left-back, lost the lurking striker and left him with a free header.

Ten Hag’s explanation was a puzzle. “When you face City, they will go up to press and so to play with Rafa [Varane on the right] and Maguire on the left – that can give problems and then you end up kicking long balls. He is better on the right, Harry, especially against teams pressing high and then you have to step in on the left, especially against [Julián] Álvarez.”

Sergio Reguilón is a career left-back yet he, too, was on the bench before replacing Lindelöf on 73 minutes when United were 2-0 down: a classic case of the gate being jammed shut after the horse has disappeared over the horizon.

City deserve copious credit for knocking United to the canvas and keeping them there. Guardiola’s side was filled with high-grade performers: John Stones, Jack Grealish, Silva, Foden, Haaland, Rodri and Álvarez deserve a special mention. Their ascendancy came after United, for a flash, were a picture of slick possession and movement.

Then, City’s attack play took over. Rodri floated a pass over the sleeping Lindelöf for Kyle Walker to turn back in, Foden headed at goal, Onana stuck out a hand, then did the same to deny a lurking Haaland by millimetres and United breathed again.

Ten Hag contended the first half was “toe-to-toe” but this was about it for United. From here City exerted a chokehold, knocking the ball between them, Grealish a reliable outlet. So when Onana, twice, sliced a long ball straight to a blue shirt Ten Hag’s exasperation was comprehensible.

Obviously discontented, the Dutchman refused to comment about the penalty Paul Tierney awarded after viewing the pitchside monitor on the instruction of the VAR, Michael Oliver. At a free-kick floated in on a diagonal from the right Højlund gripped Rodri, who went down in the area. After Tierney’s decision – it appeared correct –Haaland rolled the ball to Onana’s left and City were ahead.

Before the kick Guardiola had a long chat with Stones and Walker. What he would not have instructed was for Foden to make a backpass that was a perfect through ball for Højlund, who burned in chasing instant redemption before he was forced wide and the hope died.

After the break came City’s second-half show which a flailing United could not stop and, so, for this observer there is no doubt: Ten Hag’s team are going backwards from the edition that finished third and claimed the Carabao Cup last season.

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By the close those with blue blood inside Old Trafford had another chant to torment their opposite number with, saying United’s fans were watching the champions and would then clear off home. Many had left by then and you could not blame them.

Before kick-off the Stretford End held up a banner about Charlton that said: “The finest English footballer the world has ever seen”. How United could have done with his supreme talent.