Brentford manager Thomas Frank hailed a stunning 2-1 win at Manchester City as the Bees' biggest ever Premier League victory as Ivan Toney struck twice to bounce back from missing out on the England World Cup squad.
Pep Guardiola warned before the game that his stars could have "one eye" on staying injury free before the World Cup and his fears were realised as the champions slipped to a first home defeat since February.
Brentford had failed to win away from home in the league all season, but were good value for all three points.
"Mind-blowing performance," said Frank. "Speaking to some people from the club, this is probably the single biggest ever result, against one of the richest clubs in the world, and we have one of the lowest budgets in the division."
City could now go into the World Cup five points off the top of the table should Arsenal win at Wolves later on Saturday.
"The best team won. We struggled from the beginning and we couldn't deal with their long balls," said Guardiola.
"We didn't have the dynamic today because we were dictated by long balls that we were losing.
"We have done exceptional in the Champions League and well in the Premier League. We'll come back and prepare for the second-half of the season now."
Guardiola's concerns did not stop him naming a starting line-up containing 10 players going to Qatar.
- Haaland upstaged -
Erling Haaland was the only exception as Norway failed to qualify and he returned to the starting line-up for the first time in six games due to a foot injury.
But Haaland was for once upstaged by his opposite number as Toney produced the perfect riposte to being overlooked by Gareth Southgate.
The Brentford captain headed in his 10th goal of the season when he beat Aymeric Laporte to Ben Mee's flick on from a free-kick.
Going behind awoke the hosts from their slumber but frustration grew inside the Etihad as a series of VAR reviews for penalties were waived away.
Rico Henry escaped the biggest claim as his handball took place just outside the area, while Haaland and Kevin De Bruyne were adjudged to have gone to ground too easily.
City did finally level in first half stoppage time as Phil Foden connected perfectly on the half volley to drill a De Bruyne corner into the top corner.
The start to the second period was disrupted by a seven-minute stoppage for Aymeric Laporte to receive treatment on a head injury.
Laporte played on with several bandages covering a cut and he came to City's rescue with a remarkable goal line clearance to deny Bryan Mbuemo a tap in from Henry's cross.
City struggled to find their usual passing rhythm but did cut Brentford open with one stunning team move that Ilkay Gundogan should have finished after exchanging a one-two with Haaland.
Toney looked like he may have missed his chance to win the game when Ederson spread himself brilliantly to narrow the angle in a one-on-one and block at his near post.
But City were caught out by a clinical counter-attack from the visitors as Yoane Wissa and Josh Dasilva combined to tee up Toney to tap home eight minutes into added time.
Toney should then have had a memorable hat-trick to savour only to be denied by De Bruyne chasing back to clear off his own line.
"You get a big disappointment but the critical thing is why we love football, the next day, the sun rises and we move on again," added Frank.
"Ivan needs to continue performing and maybe there's an injury today. Maybe that's his chance to go to the World Cup?"