City's foundations crumbled again as Christian Norgaard's late header halted a resurgence as the Premier League champions relinquished a two-goal lead to draw 2-2 with Brentford.
With less than ten minutes left before Brentford's late counterattack, Guardiola's team already led 2-0.
Manchester City's captain Kevin De Bruyne produced a captain's performance and crossed perfectly for Phil Foden's close-range opener as City returned to their former masters, only to collapse in the final moments. Once again it exposed how far they had come. This season has fallen off.
They looked to have repelled Brentford's threat when Foden added another goal inside the six-yard box and continued his personal recovery 12 minutes after his first goal, with Savinho's shot missing. Erling Haaland also failed to aim his header directly at the goal post. , they probably have.
But their defensive weaknesses saw them agree to the purchases of Lens' Abdulkodir Kusanov and Palmeiras' Vito Reis, only to quickly step back up and let Brentford De returned to the game.
With eight minutes remaining, Nathan Ake's header failed to clear Mads Roerslev's cross and the ball was passed to Jon Visa. Yoane Wissa), who made a clever turn and scored his 11th Premier League goal of the season.
In stoppage time, Norgaard beat Manuel Akanji and Kean Lewis-Potter collected the ball as Brentford pushed forward to blow the roof off the Gtech Community Stadium and once again let last season's The Premier League champion suffered a bloody nose.
Sky Sports' Ron Walker at Gtech Community Stadium:
Ultimately, this is a role game. Brentford has it, Manchester City doesn't.
Judging from the 2-0 lead, Manchester City should have seen the result of the game. They had a chance to win but didn't have the mental strength.
Games like this show Guardiola how many problems he still needs to solve beyond just replacing Rodri.
There were brief glimpses of the ancient city when Kevin De Bruyne pulled the strings and Phil Foden scored, but they were fleeting. The city of the old days, even the City of September, would not collapse like this.
Guardiola countered that his side had never produced so much against the Bees, but they also didn't give up 18 shots. Most of these came before City's goal, but the first spurt of momentum from Eoin Wiesa's comeback goal was enough to topple them again.
Their fragile midfield did continue to bring pressure, but Manuel Akanji and Nathan Ake were capable of winning headers in their own box. They are not the only ones responsible for the goals, nor the only ones working within themselves.
The underlying numbers contradict any notion that City might be back, and now their fragile mentality confirms it.
Manchester City head coach Guardiola:
"What I missed today is we didn't make the right decisions in the last third when the action was something we could have run with. We won the long ball and could have run with them but we didn't Make the right decision.
"I liked the way Brentford played, we created a lot of chances today, we've been here many times and they had more chances than us.
"At 2-0 we had to level the score but we didn't have specific players to defend the result in the box - we had to do it with the ball, create and control in the final third "
brentford head coach Thomas Frank arrive TNT Sports:
"I just say to the players there, I'm really happy and proud of the performance. I think it's the first time in four years that we've gone head-to-head against the top three clubs for 90 minutes.
"I think Manchester City, Liverpool and Arsenal are the three best clubs we've had in the four years we've been in the Premier League, so they have the quality and the mentality to do that and showed bravery throughout the game and are very proud of that and of course Coming back from 0-2 down is a wonderful mentality.
"I'm happy. I'll still be happy with the performance, but it feels a little better when you get something out of it."