Claude Puel had punched the air at the final whistle, albeit in his customary understated way, with this a result that should choke the criticism, so regularly flung his way, for a while at least. Leicester City had not won here since back in 2000 but, by checking Chelsea’s recent surge of optimism, his position suddenly feels assured heading into Christmas. The Frenchman might find that a rather unfamiliar sensation.

This was such a timely triumph, a display that allied commitment and defensive discipline with industry and real threat on the counterattack. It was almost a throwback to better times, though, in truth, City have hardly looked a side on the slide this season. They are restored to the top half, and even the non-selection of Jamie Vardy for the League Cup quarter-final defeat to Manchester City – and that only on penalties – in midweek appears less of an issue now given the striker, fit after recent groin trouble, sprung forward to plunder the only goal of this game.

“I have nothing to justify,” said Puel, around whom the familiar criticisms over playing style and training intensity have swirled. “I try always to do my best to get the right balance to protect some players, get the best out of others and put a team on the pitch with the ability to win the game. If we’d won at Crystal Palace last weekend, we’d have been seventh in the table. We lost and were 12th, it’s just so tight. But our performance against City was very encouraging and, if Chelsea did not respond today, that is down to my players.” It was certainly not the display of a team whose faith in his methods had withered.

Leicester’s willingness to scrap and compete would claim the day. The midfield unit was abrasive and industrious, Ben Chilwell was a force of nature down the left, and the backline heaved to thwart Chelsea’s attempts at revival. When Eden Hazard threatened to wriggle through, five City players swarmed round him to choke his dribble on the edge of the six-yard area. “We pressed them, defended well and created chances,” said Chilwell. “The result builds confidence. We know we have a brilliant squad, we know how good we are.”

In contrast, Chelsea are still finding themselves. A first home defeat of his tenure confirmed what Maurizio Sarri must have suspected: that his team remain a work in progress, even if the panic that set in once they had slipped behind disturbed the head coach. “The reaction was, for me, strange,” said Sarri. “Not in the right direction. Not as a team. But as 11 different players. So it was really very strange. I think we could have done better in the reaction. We had only to continue to play as [we had] in the first part of the match. There was time to score without a reaction as a team shocked, a team in mental confusion.”

Chelsea struck the woodwork twice, and both Hazard and Marcos Alonso might concede they should have scored having glided unchecked into space, but were otherwise rather lacking in punch. The experiment of utilising Hazard as a false No 9 backfired this time, and they craved more of a focal point to that front line. Maybe this will intensify efforts in next month’s window to conjure some firepower. There have already been talks with Juventus and Milan over Gonzalo Higuaín, the Argentina forward who has already worked under Sarri and is on loan at San Siro from the Turin club. That arrangement could potentially be cancelled, with the Rossoneri apparently open to the idea of taking Álvaro Morata for the rest of the campaign.

David Luiz bites the net in frustration after missing a chance to score. Photograph: Clive Rose/Getty Images

A certain amount of wheeling and dealing will be required but, on occasions such as this, even Sarri must crave a striker such as Vardy to shift a contest’s momentum. For all Chelsea’s monopoly of the ball, it would take fine saves from Kepa Arrizabalaga to deny Wilfred Ndidi and Marc Albrighton but, in between, Vardy had made his decisive intervention. The goal owed much to Ricardo Pereira’s muscular burst forward and James Maddison’s composure, the playmaker capitalising on Antonio Rüdiger’s slip to prod Vardy into space, with his finish thumped inside Kepa’s post. The goalkeeper had been left flat-footed and hopelessly exposed. He deserved better. Chelsea, probably, did not.