Tariq Lamptey delivered a high-octane performance against is former club down the right flank.
Brighton played some impressive football and never looked daunted by the task against the European Champions - in fact Graham Potter's team relished it.
Hakim Ziyech lashed Chelsea ahead against the run of play in the 28th minute.
The Blues had struggled to make an impact in the game before Ziyech made space just outside the box to unleash a low, left-footed strike into the bottom-right corner.
Seagulls goalkeeper Robert Sanchez got a hand to the shot and possibly should have kept it out.
Brighton deservedly levelled on the hour courtesy of a thumping header from stand-in captain Adam Webster.
Alexis Mac Allister delivered an inswinging corner from the left and the unmarked Webster powered a header past Chelsea goalkeeper Kepa Arrizabalaga from around eight yards.
Who shone and who struggled for Thomas Tuchel's team?
Kepa Arrizabalaga: 6
The goalkeeper was quick off his line to collect and shield loose balls in the first-half. The Spaniard pulled off a fantastic save to prevent the Seagulls equalising earlier in the second half.
César Azpilicueta: 6
Azpilicueta made a number of darting runs down the right throughout the game. His movement often forced a Brighton player to track his run, hence creating space in the middle.
Thiago Silva: 7
The Brazilian's quality was never in doubt but Silva continued to prove why he is an integral part of Chelsea’s defense. Silva often popped up in the box to squander Brighton’s chances.
Antonio Rüdiger: 6
Although Brighton controlled play for periods of the game, the German was calm on the ball and wasn’t afraid to drift forward.
Marcos Alonso: 6
Despite failing to contain Tariq Lamptey at times, Alonso looked like a threat in the final-third and provided a couple of dangerous crosses.
N'Golo Kanté: 8
The World Cup winner is often mentioned as one of the best players in the world and Kante showed why he is held in such high regard. The midfielder dictacted play for Chelsea and played a number of important passes.
Jorginho sat deeper to allow Kante to push up the pitch but the Italian was important for Thomas Tuchel’s men as he played some good passes and remained calm under pressure.
Mason Mount: 6
The English midfielder had a relatively quiet game as Chelsea struggled to create clear-cut chances.
Hakim Ziyech: 8
The midfielder scored a fantastic goal against the run of play - although it could be argued that Robert Sánchez should have done better. The former Ajax man continued to show flashes of brilliance throughout the game.
Callum Hudson-Odoi: 6
Chelsea looked set to double their lead in the first-half when the winger was played through on goal, but Hudson-Odoi couldn’t keep his shot from blazing over the crossbar. Overall, the winger had a relatively quiet game.
Romelu Lukaku: 5
Lukaku was involved in an ongoing battle with Dan Burns throughout the game, with the Brighton man often coming out on top. The former Manchester United striker did play a couple of good pases but often found himself falling out of the game.
Mateo Kovačić: 6
The substitute did get involved with a couple of passes but failed to impact the game.
Kai Havertz: 6
Havertz was unable to threaten Brighton’s defense after coming on for Lukaku.
Timo Werner: 6
The German striker couldn’t make a difference after coming on from the bench.