LONDON • As Pep Guardiola prepares to take his spending on defenders to over £400 million (S$708.6 million), his side's 5-2 capitulation against Leicester showed that Ruben Dias' impending arrival alone might not be sufficient to solve their defensive issues.

It was the first time in 686 games that a team managed by Guardiola conceded five goals, with Jamie Vardy becoming the only player to score two hat-tricks against sides led by the former Barcelona and Bayern Munich boss.

City went ahead at the Etihad after just four minutes thanks to former Leicester forward Riyad Mahrez's thunderous strike. But that was as good as it got for City as Vardy tore their creaky defence to pieces with his pace and movement on Sunday.

He won two penalties on a night when Eric Garcia, Kyle Walker and Benjamin Mendy committed identical mistakes, getting caught out to concede three spot-kicks.

Vardy converted both penalties either side of a classy back-heel finish, while James Maddison added a fourth. Youri Tielemans completed City's embarrassment with a late penalty after new signing Nathan Ake scored his first City goal.

Guardiola rued his team's lack of composure but vowed to bounce back after City conceded five goals in the league at home for the first time since a 5-1 defeat by Arsenal in February 2003.

"It's a tough result but I am not going to give up. I am going to find solutions for the team to be stable," said the Spaniard, who had attempted to protect his backline by deploying Fernandinho and Rodri in front of them.

"My players might have thought that they weren't playing well enough after conceding the equaliser but we were well on top at that stage. The problem was that we put extra pressure on ourselves to score the second and third.

"We need to be more calm, we don't have the players to attack the box that we need."

With both natural strikers Sergio Aguero and Gabriel Jesus out injured, City looked toothless despite having the lion's share of the possession. Former Manchester United midfielder Darren Fletcher believes the lack of a recognised finisher had a knock-on effect on their overall display, and with the duo set to remain unavailable for weeks, City have more puzzles to solve.

"Pep usually goes with a single pivot as part of a 4-3-3," he told the BBC. "But with the players he had available, he went with two holding midfielders... and moved Kevin de Bruyne to more of a No. 10 position, behind Raheem Sterling who was playing as a central striker.

"City had three, four or even five players out of position - or at least not playing in their best position - and, on top of that, their full-backs never offered anything attacking-wise down the flanks."

Another mitigating factor was the absence of their No. 1 centre-back Aymeric Laporte, who was only fit enough to make it to the bench, with his new partner set to be Dias once his move from Benfica is ratified.

The Portuguese club revealed they have agreed a deal to sell the 23-year-old for €68 million (S$108.9 million) plus add-ons, with City's Nicolas Otamendi going the other way in a separate transfer for €15 million.

Dias made 137 appearances during a four-year spell with Benfica, winning the league title last year.

Former England defender Gary Neville said Guardiola is facing the biggest challenge of his career with City's defence despite managing to add the Portugal international, who was part of the side that lifted the Nations League trophy last year.

"Some of the wounds from last season are reappearing. The bugs that cost them the title," he told Sky Sports. "Certainly, you can get at this Manchester City back four a lot quicker that you could previously. They don't seem to react in transition higher up as they did."

REUTERS, AGENCE FRANCE-PRESSE