Brentford held on for their third Premier League win of the season as goals from Ethan Pinnock and Bryan Mbeumo sank a wasteful Chelsea in the West London derby at Stamford Bridge.
The Blues, who missed several chances, were punished through Pinnock’s thumping header from Mbeumo’s wicked cross.
With Chelsea goalkeeper Robert Sanchez up the field for a late corner, Neal Maupay led a Brentford counter-attack and set up Mbeumo for the second.
Chelsea, who went closest in the first half when Noni Madueke struck the woodwork, slipped to a ninth home defeat this year thanks to some poor finishing.
Brentford keeper Mark Flekken was never truly stretched and the visitors defended resolutely before hitting Chelsea on the break.
Victory lifted Brentford to 10th in the table, one point and one place above Chelsea.