Chelsea fell to a third home defeat of the season as Brentford maintained their 100 per cent winning record at Stamford Bridge in the Premier League with a deserved 2-0 victory.
Ethan Pinnock took advantage of non-existent marking to head the visitors in front shortly before the half-hour mark after Mauricio Pochettino's side had failed to take advantage of a first half in which they dominated.
Thereafter there was little genuine attacking threat nor hope of salvation, as the hosts took a worrying backwards step towards the goal-shy, hesitant play that characterised the manager's early games.
Robert Sanchez was embarrassed in added time after joining his team's attack for a corner, failing to catch Neal Maupay in a foot race as he broke with the ball, allowing Bryan Mbeumo to score in an empty net to compound home fans' woes.
Chelsea's dire form at Stamford Bridge now stands at one win in their last 13 games in the league, with August's victory over Luton their only success here in seven months.
They were without Enzo Fernandez and Mykhailo Mudryk, key components in their recent uptick in form, with neither player risked after picking up knocks in training on Friday.
In place of Mudryk came Noni Madueke, in for his first start under Pochettino, and he wasted little time in staking a case to his manager, standing up Vitaly Janelt on the right of the penalty area and opening his body to unleash a wicked, bending effort that thumped the crossbar.
It was a busy start from Chelsea. Conor Gallagher, captain again with Reece James fit only for the bench, stung the palms of Mark Flekken when he shot low at goal from 30 yards.
Marc Cucurella found space from a wonderful ball into the box from Cole Palmer, but the defender could summon neither power not placement with his right foot.
Raheem Sterling looked in electric mood. His dazzling burst through the middle saw the ball break to Madueke, who shepherded it inside for Palmer to return for Sterling who had continued his run. The move deserved a goal; instead the England forward ballooned his shot into the Matthew Harding Stand.
As the half wore on Chelsea became increasingly camped in the visitors' half, shifting focus from probing for the critical pass in central positions in favour of balls down the channels, where Madueke and Sterling would not allow Brentford peace.
But there was a feeling of old habits creeping into Chelsea's play, with the creative fluency of recent weeks not so forthcoming. The period ended with Pochettino remonstrating with a fan who questioned Nicolas Jackson's lack of involvement, the manager of a mind that only supportive voices were welcome, but doubtless aware privately of his team's shortcomings.
There was almost a goal within minutes of the restart, Janelt left to rue profligate finishing after he was left free 12 yards out but fired straight at Sanchez. It was a stark warning, but one Chelsea's defence would not heed.
On 58 minutes, their generous marking struck again and this time Pinnock readily accepted the gift.
It was a smart link-up between Kristoffer Ajer and Mbeumo from a throw-in on the right that began the move, with Mbeumo given space to run the ball to the byline and hoist a cross. The delivery hung high in the air, finally dropping into the six yard box where Axel Disasi did little more than observe as Pinnock powered beyond him and beat Thiago Silva to the ball to thump his header home.
The shock jolted Chelsea from whatever rhythm they had inherited from the first half. Still they hogged the ball, but rarely was Flekken tested as they toiled in vain for an equaliser.
Substitute Yehor Yarmolyuk should have made it 2-0 on the break in the final minutes, he was denied point-blank by Sanchez, before Mbeumo lashed millimetres wide of the post.
Pochettino's assistant Jesus Perez was sent off with frustrations between the two benches boiling over, and it got even worse for the home side with Mbeumo's tap-in and the end of Chelsea's mini-revival.
