The players emerged for the start of the game when the home fans played Beatles classics "Hey Jude" and "Hey Judas." Graham Potter was not in any doubt about what he would see when he returned to the Seagulls.
A chastening and hugely embarrassing afternoon for the 47-year-old coach, who leftBrighton abruptly last month after a hugely successful three-year spell to replace Thomas Tuchel. His first defeat as Blues boss and the first win for his successor on the south coast were both on Saturday.
The prospect of making a point to Potter that the step up he had taken did not elevate him to an "untouchable perch" was wonderful. This wasn't just about Potter. The defender who handed in a transfer request to join Manchester City before they paid a higher transfer fee was booed by the crowd. He didn't take an early throw in.
You can watch LaLiga, Bundesliga, MLS, more on the US version of the network.
A flow of talent which angered the home fans has been a feature of the seven coaches, staff and players who have traded BRIGHTON for CHELSEA.
Potter did not have any expectations. I don't have anything to apologize for. I did well. The team is a great one. They were fourth from the bottom in the league.
There's a lot of money raised through player sales. I hope the next manager does a great job for them.
Potter should be alarmed by the fact that this was his own fault. The advanced deployment of Christian Pulisic and Raheem Sterling as wing-backs made the 3-4-2-1 system look more like 3-2-4-1.
Solly March and Pervis Estupinan were forced into one-on-one situations against the wider trio of centre-backs as a result of Seagulls' sharper and more assertive start to the game. In the first half, the system offered high risk and reward. They were so easy to play against that they were able to score three goals in the first 45 minutes of the game.
There is a report on the table and upcoming matches.
The damage had already been done when Potter switched to a 4-1-5-1 with Ruben Loftus-Cheek at right-back.
"The responsibility for the wing-backs wasn't to defend against their wing-backs but I understand that whenever you do something and it doesn't work, you look a bit of a fool." It's how it is. I have to do better.
The feeling of being shot in the foot grew from the beginning. They had to clear the line twice by the time they fell behind.
Silva gave the ball away and Kaoru was going towards the box. He slipped a clever pass for Leandro Trossard, who kept his composure to round Kepa Arrizabalaga and fire low into the net.
Home fans sang "Potter, Potter what's the score?"
There were two own goals. He diverted March's 14th-minute corner into his own net after sticking out a knee. Estupinan got in down the left and crossed in one of the examples. He turned the ball into his own net.
"You're getting sacked in the morning," rained down from the stands as supporters continued to target Potter, who stood arms folded on the touchline, seemingly in disbelief at how his side were capitulating. Cheers rang out when the replays of Chalobah's mistake were shown.
Even before the break, they had opportunities of their own. Robertnchez saved the day for the Seagulls when he saved a volley from Pulisic. The ball was palmed away by the keeper from the left-wing delivery.
The risk-reward ratio wasn't in their favor. Potter abandoned the 3-4-2 shape in previous league games and was forced to do the same here. The second-half improvement was a direct result of Loftus-Cheek, yet it was clear how much they missed James.
Three minutes into the second period which began with Mendy replacing Kepa in goal because of a foot problem, Kai Havertz headed home a fine cross from Gallagher.
The proceedings began to be dictated by the Blues but they only worked intermittently. The Spaniard was forced into a diving stop by Pierre-Emerick in the 20th minute. Havertz scored after good work on the right from Loftus-Cheek. But it was the Seagulls who had the final laugh, as Mendy saved from Enciso only for Gross to score the rebound.
Prior to this game, Potter's team had allowed four goals. When the heat of battle had passed, several of his former players embraced Potter, who was warmly embraced by them.
It was a pleasant moment on a dreary day. Potter needs to consign this to history the same way BRIGHTON did with him.