Brighton’s intent was clear from the off, Thiago Silva gifting them the ball from a goal kick before scuttling back to clear Leandro Trossard’s lob off his line.
Silva was called on again to head away Pervis Estupinan’s goalbound effort before he surrendered possession on four minutes to allow Kaoru Mitoma a run at goal, the Japanese winger slipping in Trossard to round Kepa Arrizabalaga and fire in the opener.
It was two inside the quarter-hour mark as a corner from the right was clumsily diverted home by Ruben Loftus-Cheek’s knee.
Chelsea should have made an instant riposte as chants of “you’re getting sacked in the morning” reverberated from a record Amex Stadium crowd but Conor Gallagher fluffed his lines in a one-on-one before Christian Pulisic skewed his rebound wide.
Robert Sanchez pulled off a fine save to deny Gallagher’s flicked header before Chelsea’s reply fizzled out.
It was 3-0 on 42 minutes when Estupinan arrived unmarked on the counter and had his low cross slid home by Trevoh Chalobah.
Potter stuck with the same outfield XI for the second half, swapping out Kepa Arrizabalaga for Edouard Mendy due to injury, and earned a quick reward.
Gallagher’s perfect cross from the right was headed in at the far post by Kai Havertz to put Chelsea back in the game only 90 seconds after the whistle.
Ben Chilwell and Pierre-Emerick Aubameyang were introduced after the hour mark as the visitors failed to build any serious momentum, relying only on half chances as the clock ticked down.
The last ten minutes saw Hakim Ziyech and Armando Broja brought on but Chelsea were unable to test Sanchez any further, Brighton wrapping up the win as Pascal Gross turned home a rebound from debutant Enciso’s effort.