Chelsea manager Graham Potter suffered a nightmare return to former club Brighton as his side were outclassed by the Seagulls at the Amex.
Thiago Silva had already been forced to head two Brighton chances off the line by the time Leandro Trossard opened the scoring after just five minutes on the south coast.
Potter's afternoon then went from bad to worse as he saw Ruben Loftus-Cheek score an own goal before Trevoh Chalobah also left Kepa Arrizabalaga picking the ball out of his own net before half-time.
The Chelsea boss, who was roundly booed, made changes at the break and did see Kai Havertz pull one back shortly after half-time to offer the Blues hope of a comeback.
Brighton were not to be denied, however, as they held on to claim all three points and even scored a fourth late on to hand Potter his first Premier League defeat since taking charge at Stamford Bridge.