Graham Potter's return to Brighton turned into a nightmare when he suffered his first defeat since taking charge of Chelsea as the hosts deservedly took the spoils at the Amex Stadium .
Potter left Brighton to succeed outgoing coach Thomas Tuchel at Chelsea last month, returning to the south coast to face his former employers for the first time complete with a nine-match unbeaten record in all competitions at his new club.
But the hosts made a blistering start at the Amex Stadium against Potter's bewildered side, racing into the lead inside five minutes through a well-taken Leandro Trossard goal.
Breathless Brighton kept coming and soon had a quickfire second after Ruben Loftus-Cheek diverted a corner into his own net, with another own goal from Trevoh Chalobah making it three for Brighton three minutes before the interval.
Chelsea started well after the break and got back in it three minutes into the second half through Kai Havertz's header, but the damage had already been done and Potter's team could not rouse a comeback.
Pascal Gross's last-gasp fourth goal capped a fine afternoon for Potter's successor Roberto De Zerbi, with the first win of his reign moving Brighton up to seventh in the standings, while Chelsea stay fifth, eight points behind leaders Manchester City
Premier League
soccer
Chelsea
Sport
Thomas Tuchel
Kai Havertz
Leandro Trossard
Roberto De-Zerbi
Brighton