To put the scale of this shock result into some sort of context, Arsenal had been able to score four goals in their previous 10 Premier League matches – a sequence that had brought them five points. It had the club mired in their worst start to a season since 1974-75 and the manager, Mikel Arteta, in crisis. One of the big pre-match questions concerned whether Arsenal were in a relegation battle.

This was a restorative result and performance, with Arteta’s bold team selection returning a rich dividend. He gave first league appearances of the season to Pablo Marí and Emile Smith Rowe and a first start in the competition this time out to Gabriel Martinelli. Smith Rowe emerged with honours, driving from his No 10 role.

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Arsenal were in control by half-time, with Alexandre Lacazette’s penalty being followed by an absolute banger of a free-kick by Granit Xhaka, who is one of the players that the Arsenal support love to hate. On his comeback from suspension, Xhaka was excellent.

Bukayo Saka got the third and the crazy thing was that Arsenal could have scored more, with Martinelli twice working Édouard Mendy and Lacazette almost punishing the goalkeeper for a loose pass out. Mohamed Elneny also rattled the crossbar.

It would not be Arsenal without a wobble. After the Chelsea striker, Tammy Abraham, had converted a cross from one of their substitutes, Callum Hudson-Odoi – the goal was given when VAR overruled an offside against Abraham – the visitors pushed.

Chelsea had barely turned up in the first half, with Frank Lampard lamenting their failure to do the basics like sprinting and pressing. They were passive to the point of lethargy both on and off the ball. But after an improved second-half showing, they set about fashioning an escape route.

Thiago Silva headed wide when gloriously placed and Arsenal looked to be entering panic stations when Marí was late into a challenge on Mason Mount, leaving another substitute, Jorginho, to address a penalty in the first of five added minutes. Arsenal could not mess this up, could they?

Chelsea’s revival floundered when Bernd Leno kept out Jorginho’s spot kick and Arteta could drink in the elation and relief. Nothing is easy for him, at present, and he had to plot a course to victory without the majority of his Brazilian contingent. David Luiz and Willian were ill while the defender Gabriel has been forced to self-isolate after coming into contact with somebody who has recorded a positive Covid test.

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What pleased Arteta was how his players embraced the pressure of the situation; the energy they brought from the first whistle. Arteta had reverted to a 4-2-3-1 system, having started with 3-4-3 in the previous three games in all competitions, and there was a fearlessness about the youngsters in the line behind Lacazette; a verve about their movement. From right to left, it read Saka, 19, Smith Rowe, 20 and Martinelli, 19. They more than repaid their manager’s faith.

Mount grazed the outside of a post with a curling free-kick on 12 minutes after Xhaka had tripped Christian Pulisic but the first half was almost all Arsenal. Martinelli scuffed wide after just 44 seconds following a burst up the right by Héctor Bellerín and Smith Rowe wasted a fine chance on 25 minutes, allowing a low Bellerín cross to come across his body and failing to get a clean contact with his left foot.

Arsenal had the lead when the outstanding Kieran Tierney took a fine first touch following Xhaka’s pass to cut inside Reece James. With position inside the area, Tierney knew that the slightest touch from the Chelsea right-back would add up to a penalty. He felt it and went down and, if it looked a little soft, the law of these moments lies in the contact. Lacazette’s conversion was nerveless.

Arsenal’s second was all about the technique of Xhaka. Saka’s slicing run inside had forced N’Golo Kanté to trip him and when Xhaka sized up the free-kick his sights were fixed on the near top corner. He picked it out with a beautifully flighted left-footer that had Mendy clutching at thin air.

Lampard replaced Mateo Kovacic and Timo Werner at half-time, with the latter having been particularly disappointing. There were plenty of other contenders to be hooked. Chelsea were better but they were 3-0 down when Saka shaped what looked like a deep cross from the right and saw it drop in off the far post. “I saw the keeper off his line and thought I could chip him,” Saka insisted.

It meant Chelsea were on their way to a third defeat in four games and a visibly furious Lampard had plenty to occupy him. Arteta simply described it as a really important win: “It was convincing and shows we can do it when we are at our best.”.