Trevoh Chalobah and Nicolas Jackson head Chelsea to win against Tottenham

Ange Postecoglou says he does not care about the questions being asked about Tottenham’s inability to defend securely from set pieces. The manager believes he will get it right. But he could not avoid another hail of them after his team slumped to a third defeat on the spin, their season in increasing danger of fizzling out. And it was some way from being Spurs’ only shortcoming.

It was Chelsea’s night, this a victory to fire their hopes of a Europa League finish. They were excellent in the first half, Spurs so poor that Postecoglou howled in frustration on a number of occasions. It was difficult to remember seeing him so unhappy.

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And, after what had happened in Sunday’s derby defeat at home to Arsenal, there was a certain inevitability about how Spurs were unhinged. Arsenal had profited by using Ben White as a blocker on corners against the goalkeeper, Guglielmo Vicario. Here, it was Marc Cucurella setting a screen to take out Brennan Johnson and enable Trevoh Chalobah to reach Conor Gallagher’s free-kick and head Chelsea into a 24th-minute lead.

It was the 15th set-piece goal that Spurs have conceded in the Premier League this season and No 16 would condemn them to defeat on 72 minutes. Cole Palmer’s free-kick beat Vicario and crashed down off the underside of the crossbar, Nicolas Jackson reacting sharply to loop the rebound home with his head. Only three teams in the league have conceded more set-piece goals than Spurs.

Mauricio Pochettino could toast the fight of his Chelsea players on the occasion of his 400th game as the manager of an English club; their work without the ball as much as with it.

Spurs, by contrast, were left to sift through the wreckage of a performance that fell woefully short of the required levels – especially in terms of conviction and aggression.

It feels like a long time ago that Spurs were top of the league after 10 matches with eight wins and two draws. They have taken 34 points from the 24 games since then – bang average mid-table form. Before Arsenal, they had crashed 4-0 at Newcastle. Next for them is Liverpool at Anfield on Sunday.

This is a fixture that normally stirs the passions – remember Chelsea’s 4-1 win at nine-man Spurs last November, which had such repercussions for Postecoglou’s team – and there was a pointed moment before kick-off when a group of home fans unfurled a giant banner of Gallagher. “Chelsea since birth,” read the caption. The subtext: Do not sell him in the summer. Especially not to Spurs.

It is easy to see why Postecoglou would want Gallagher. No player has made more ball recoveries in the final third than him during the league season; he would be ideal for Ange-ball. Gallagher was behind plenty of Chelsea’s good moments during a one-sided first-half, starting when he robbed Pape Sarr, leading to Mykhailo Mudryk releasing Jackson up the inside left.

Jackson had Vicario to beat and, although the goalkeeper got something in the way of the shot, the ball was rolling in until Micky van de Ven got back to clear from in front of the line. He blasted at Palmer, who could not react in time, the ball going off his boot and over the crossbar.

Postecoglou would rage at regular intervals during the first half. Chelsea dominated, Gallagher setting a high bar with his hustle, Noni Madueke and Mudryk menacing on the wings. Spurs were so loose with their passing, particularly when they tried to build from the back. Where was the structure? Or the self-belief? There would be boos from the travelling support upon the half-time whistle.

The breakthrough had been advertised, Alfie Gilchrist and Madueke going close with shots, and it had to be a set piece. There would be a long VAR check to see whether Cucurella had been offside or committed a foul on Johnson. He was cleared on both counts.

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Chelsea could have been out of sight, Mudryk curling inches past the far post on 33 minutes before Spurs stirred. Cristian Romero headed just wide from a Pedro Porro free-kick and there were flickers from Sarr and Johnson. The former almost got in only to be thwarted by a Chalobah block.

Pochettino has had serious injury problems this season but never as bad as those here, the number of casualties numbering 14. Postecoglou, dealing with issues of his own, had been forced to play Emerson Royal out of position at left-back. He had recalled Yves Bissouma and dropped James Maddison.

Spurs were better after the interval, pressing on to the front foot. They hinted at something, although they did not create anything clear-cut. Palmer had gone close twice when his free-kick led to Jackson’s goal, the feeling that it would not be Spurs’ night gathering steam when Johnson missed a glorious chance to pull one back almost immediately.

Spurs finished with a flurry of pressure in stoppage time. It was too little, too late. Most of their fans had long since departed.