Brighton & Hove Albion ruined Chelsea interim manager Frank Lampard's return to Stamford Bridge with a 2-1 comeback win on Saturday.
Substitutes Danny Welbeck and Julio Enciso scored to condemn the Blues to a third defeat in three games since the change of coach.
Lampard, who rested several first-choice starters before Tuesday's Champions League quarter-final second leg against Real Madrid, saw the Blues score the first goal of his second spell in charge when Conor Gallagher's deflected shot beat Robert Sanchez.
But the visitors were the better side for long spells, forcing Chelsea goalkeeper Kepa Arrizabalaga into fine saves and hitting the bar before they drew level when Welbeck squeezed between two defenders to head in off the post in the 42nd minute.
The Seagulls got the second goal that they deserved when Paraguayan Enciso scored with an unstoppable shot from 25 yards in the 69th minute, bolstering Brighton's hopes of European football for the first time in their history next season.
Lampard admitted he has to turn around the club's fortunes quickly.
"At the minute, we are falling short on that and we need to turn it around quickly," said the former Chelsea midfielder who was rushed in for a second spell in charge of the Blues after Graham Potter's dismissal earlier this month.
"We haven't got training time... So the response has to be what you see on the pitch, especially with Tuesday coming."
“In terms of performance, that was the most disappointing one because we were well beaten in the basics of football,” Lampard added. “Brighton are a fantastic team, and they can perform like that against anyone in the league. But we were short.
“A yard short, a tackle short, a fighting-duel moment short. When that’s not right, you’re not going to win games.”
Player ratings from the match can be seen in the picture gallery above.
