Gary Neville says Pep Guardiola is facing the biggest challenge of his career as the case for Manchester City’s defence crumbles.
Leicester exposed Manchester City's frailties to produce a stunning 5-2 win at the Etihad Stadium that casts serious doubts over the ability of Guardiola's team to regain the Premier League title.
Riyad Mahrez had given the home side the lead against his former club as Leicester struggled to touch the ball in the first quarter but when that changed, old vulnerabilities reappeared.
"They were so good in the opening 25 minutes but as soon as Leicester broke on them a couple of times, you felt that, psychologically, it just damaged them," Neville told Sky Sports.
"Some of the wounds from last season are reappearing. The bugs that cost them the title. 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."
Guardiola has sought to protect his ailing back four in the opening weeks of the season by deploying Fernandinho and Rodri to protect them in midfield.
Against Leicester, he opted to withdraw Fernandinho when chasing the game - with dire consequences - but the problems were there even before that.
It did not help that Kyle Walker, Eric Garcia and Benjamin Mendy all conceded penalties with unnecessary challenges inside the area.
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"Three different players making the same basic error," said Neville.
"Rashness. Naivety. Whatever you want to call it, it is there in that backline. Pep Guardiola is looking to see if he can defend his players but I am not sure he can.
"His defenders aren't good enough, whichever way you want to look at it. He is a great coach, one of the greatest coaches of all time. But one-on-one, once his defenders get in those positions, they are really poor. It is almost like in their mind they cannot get their head around the fact that someone has got goal-side of them.
"In those three moments that the penalties were given away, you wonder how many that Ederson would have saved. How many of the players who were going through would have hit the target? They may have still been in the game, Manchester City, but for the rash defending."
Instead, this became the first Guardiola team in his 686 games as a manager to concede five goals in a game.
"That is an incredible stat on behalf of Pep Guardiola and how good he has been, how good the teams that he has had have been, how good defensively they have been," said Neville.
"He has set the standard. Is it fair to say that as he stands on the touchline here today with no title last season, he has got the biggest job that he has probably ever had in football at this moment in time, to win the title again.
"He could go two seasons without it because they do look well behind Liverpool compared to what we saw at Stamford Bridge last week.
"We know the standard that Liverpool are setting. When you think of the business they have done in the last week. I know it is early but Liverpool will be watching this game and they will gain in confidence from this. You do.
"It is not that they will be thinking they are going to win the league because City are not at it. There is a long way to go but when you see your main rivals losing like this, it just gives you encouragement. It makes you feel stronger."
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The return of Aymeric Laporte, fit enough for the bench against Leicester, and the prospect of bringing in Ruben Dias from Benfica, gives hope that the team's defence could look very different before too long.
"I am sure he will see it as a challenge and be invigorated by it. He knows he has got Laporte to come back, potentially the signing of another centre-back in the next 24 hours. He can remodel the way that his team defends in the coming weeks and get them back to the basics that he has instilled in all those teams that have not conceded five goals in the previous 680 games.
"He has got surely. He has won so many titles. He has been so good. He has got the belief of the club behind him. There is nothing happening here in that respect. But he has got a job to do in terms of resetting this team back to a standard that he has previously reached."
'Man City a shadow of the team we know'
Sky Sports' Graeme Souness:
"City were a shadow of the team we have seen for the last few years. They are missing their 'fox in the box' and they huffed and puffed for most of the game.
"Leicester frustrated the life out of City. Anyone playing City in the next few weeks - that's the blueprint. City had five shots on target in the whole of the 90 minutes.
"Once you break the first press and get at them, you have a real chance of hurting them. City shot themselves in the foot with the penalties they gave away.
"I fancy Liverpool to retain it. When you try to apply logic to football, it can come back to bite you. I'll try to introduce some logic. Liverpool win it by 18 points, Liverpool in my opinion have strengthened big time. I look at Man City now, and whether Dias comes or anybody else, it's going to need more than that to take them from 18 points behind Liverpool.
"To a man I think we can all accept that Liverpool are stronger now than what they were 12 months ago.
"But I have to say, there is a caveat. We all get carried away, and it's our job to make these assessments, but we're three games in. Some need five or six to get fully fit, but right now, I think Liverpool again could run away with it again."
'City's defence was a shambles'
Sky Sports' Micah Richards:
"After Fernandinho went off, they capitulated. You can see by his body language, to go off at 53 minutes. He's Manchester City's best player for me.
"Man City have just become a possession-based team. I'm not blaming it just on Rodri. But he doesn't read danger like Fernandinho, and the backline get exposed time and time again.
"How many times does it have to happen before City rectify it? Everyone talks about the defence - and it was a shambles, it really was embarrassing.
"But there is more to it than that. They are weak, too weak. It's the manner of the defeat."