For all their early-season efforts, it is clear that Maurizio Sarri’s Chelsea is still a work in progress.

Leicester City came to west London with embattled manager Claude Puel looking to relieve some of the pressure that a recent run of poor results had created.

He didn’t expect to be leaving with the win after his Leicester side inflicted a shock defeat on their opponents courtesy of a well-worked goal from Jamie Vardy at the beginning of the second half. 

Meanwhile, this defeat left Sarri scratching his head, citing the “mental confusion” of players.

It ended an undefeated run of 12 matches at Stamford Bridge and meant that his side had lost further ground on Liverpool and Manchester City at the top of the league.

“I think we played very well for 55 minutes,” said Sarri. “We played very good football. After the goal, the reaction was, for me, a strange reaction. 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 in the first part of the match. There was time to score without a reaction as a team shocked, a team in mental confusion.”

Things would have been different had Eden Hazard’s first half shot that slammed the crossbar gone in. It had been a promising start for the home side, and in truth, Chelsea’s display was commanding and assured.

Even when England striker Vardy put the Foxes ahead, Chelsea had chances to get back into the match.

However, the Leicester players began to dig in, and as the match drifted to its conclusion, Chelsea’s players started to look devoid of ideas.

Full-back Marcos Alonso had Chelsea’s final opportunity moments before the final whistle, but he struck the outside of the post. Leicester had hung on for a much-needed win.

“We played like a team with a great mentality,” said Frenchman Puel. “It’s a great result but perhaps we were a little lucky at the end when they hit the post.”

Chelsea have upcoming matches to Watford, on Boxing Day, before a tough trip to Crystal Palace on Saturday.

Leicester face upcoming matches at home to Manchester City and then against Cardiff City.