Brighton made a blistering start and went ahead in the fifth minute through Leandro Trossard. Chelsea captain Thiago Silva twice cleared off his line in the opening stages, before Trossard collected a pass from Mitoma, rounded visiting goalkeeper Kepa Arrizabalaga and fired home.
Albion doubled their advantage in the 14th minute, with recalled Chelsea midfielder Loftus-Cheek diverting the ball into his own goal via the underside of the crossbar following a Solly March corner.
Chants of ‘Potter what’s the score?’ grew louder among home supporters and were swiftly followed by ‘You’re getting sacked in the morning’.
Brighton were 3-0 up in the 42nd minute after Chelsea defender Trevoh Chalobah diverted the ball into his own net following Estupinan’s pull back from the left.
Chelsea pulled a goal back within three minutes of the restart. Kai Havertz headed home unmarked following Conor Gallagher’s cross from the right.
But Albion deservedly had the last say as Pascal Gross sealed Brighton’s success by making it 4-1 in added time.
Here’s how the Albion players rated...
9. Kaoru Mitoma 7/10
Recovered from his ankle injury and made his first start as Welbeck was absent with illness. Some nice touches and tracked back and pressed with intent. A popular player with the fans and a very encouraging display. Replaced by Lamptey Photo: Alex Pantling
10. Pascal Gross 8/10
Bagged the last goal having moved into a more advanced role in the later stages. Just always does the right thing at the right time. Another sound performance from the experienced German Photo: Alex Pantling
11. Adam Lallana 7/10.
Played a very intense 65 minutes. Pressed with everything he had and calm and composed on the ball as always. Great to see him fit and firing once again Photo: Julian Finney
12. Julio Ensico 6/10
Came on for 25 minutes and did his job well at right back. Will be all the better for more minutes under his belt Photo: Alex Pantling