Manchester City suffered their first defeat of the season this weekend at Carrow Road against Norwich City.
The result is without a doubt the shock of the season so far, as the champions of the EFL Championship turned over the champions of the Premier League, and arguably the strongest side in Europe.
Here's a look at what went wrong for Pep Guardiola's men.
Defective defending
Firstly and perhaps the most obvious reason for City's defeat was the abysmal defending.
Aymeric Laporte being out injured left Nicolas Otamendi and John Stones to deal with Teemu Pukki amongst other Canaries forwards - a task they clearly failed with.
Lapses in concentration were clear on multiple occasions from both centre-backs, giving the ball away cheaply, which eventually proved costly as Otamendi gave the ball away inside his own area, leading to Norwich's third.
It'll be interesting to see if Guardiola restores his faith in Stones and Otamendi as a partnership, or looks into his other options for upcoming games.
Complacent Pep
It goes without saying that since his arrival in England, Guardiola has been a breath of fresh air for the league, and an inspiration to many in England as to how beautiful football can be played. However, did the Spaniard get it wrong this weekend?
City star man Kevin de Bruyne was left on the bench following the international break, perhaps being rested ahead of a busier schedule as the UEFA Champions League and Carabao Cup kick in for City.
The lack of creative spark that the Belgian usually brings to the side was clear from the off, with Ilkay Gundogan unable to step into De Bruyne's shoes.
He was eventually brought on with City 3-1 down, although it was too little, too late, and perhaps a reminder to Guardiola that in the Premier League, anybody can beat anyone.
Shootings boots missing
When describing the likes of Sergio Aguero and Raheem Sterling, a word that straight away comes to mind is clinical - something that City weren't at Carrow Road.
Whilst huge credit must go to Daniel Farke's Norwich for their disciplined, resilient defending, City will know that they would've won the game had the been as clinical as Norwich.
Aguero missed golden chances with his head from close range either side of half time, whilst Sterling and Gabriel Jesus also had chances you'd usually expect them to tuck away. A bad day at the office all round for the Blues.
With the talent in City's side, it goes without saying they'll bounce back. Although, Guardiola and his men will know that they have a mountain to climb already, being five points behind Liverpool, and that too many more days like they had in East Anglia will cost them their title.