Chelsea slumped to a third consecutive defeat under Frank Lampard as Brighton produced a superb display at Stamford Bridge to enhance their credentials as European contenders.
Substitute Julio Enciso hit the winner 20 minutes from time with a magnificent 30-yard rocket into the top corner, completing a stunning turnaround after Danny Welbeck’s header had cancelled out Conor Gallagher’s deflected opener for the hosts.
That at least ended the Blues’ streak of four games without a goal – their worst run in 30 years – but it will be small consolation for supporters who saw their team beaten resoundingly by Roberto De Zerbi’s visitors.
Even on their recent poor run, Chelsea have rarely been so outclassed. Brighton were outstanding, their range of passing and intelligence with the ball making a mockery of the £500million spent by Todd Boehly to try and propel Chelsea up the league. On this showing, only one of these teams belonged in Europe next season.
Minutes later, Chelsea led. Mykhailo Mudryk took possession on the left and drove infield. Feinting to play the ball wide, he slid a clever reverse ball inside to Gallagher, who strode onto it and hit a shot that deflected off Lewis Dunk and in.
Brighton, undeterred, simply went about their work. Pervis Estupinan went on a determined run down Chelsea’s left and fed the ball inside for Solly March to try his luck from range, the winger’s effort whizzing inches over.
Then Mitoma gave a reminder of his ever-rising stock by dancing through the defence and drawing an outstanding one-handed save from Arrizabalaga.
There were further chances for Mitoma and Mac Allister as the visitors slowly took control of possession and of the game, though both missed the target from promising positions.
Soon Brighton were in total charge, and after 30 minutes they went close again.
Ferguson took the ball from a throw-in and fed substitute Enciso, on for the injured Joel Veltman. He slipped his man and crossed for Ferguson who, having continued his run, placed a header towards the corner, only for Arrizabalaga to fling himself into another superb save to turn it over the bar.
Ferguson, who had been excellent, injured himself in the process and was replaced by Welbeck.
For Brighton it proved a blessing in disguise. They equalised within minutes. The ball was worked out wide to Pascal Gross who looked up to see Welbeck peeling away at the far post. The cross was inch-perfect, and as two Chelsea defenders rose neither could beat Welbeck to the ball and stop him heading Brighton level.
The second period started in the same vein. Mitoma again tormented Chelsea down the left, and slipped in Enciso who almost gave Brighton the lead but for Arrizabalaga’s block.
Chelsea needed a change. Lampard responded by making four at once, seeking to swing the balance back his team’s way.
If anything, it destabilised them further. On the hour mark Enciso dropped a hint of what was to come, outmuscling Chalobah and substitute Reece James and striking the post.
Then came his moment. There seemed little on when he collected March’s square ball 30 yards out. Chelsea gave him space, failing to take the threat seriously and Enciso made them pay in spectacular fashion.