Chelsea fell behind Brentford for their first loss since 1939 as Christian Eriksson propelled the Bees to a 4–1 victory that should seal their Premier League existence.
The European champions were exposed through a sensational long-range strike from Antonio Rudiger at Stamford Bridge at the start of the second half, but they fell for the first time as owner Roman Abramovich was hit by UK government sanctions.
Just a minute later, Vitaly Genault raced for the visitors to score three goals in 10 minutes.
Ericsson has been in good form since returning to competitive football after suffering a cardiac arrest on the field during Euro 2020.
The former Tottenham midfielder scored twice in as many games during his international return for Denmark and continued his scoring streak by picking up the ball at Edouard Mendy to complete the turnaround.
Genault made it 3-1 with a brilliant dink over Mendy at the hour mark.
Third-placed Chelsea are set to break into the top four but will need a major improvement to travel to Real Madrid in Tuesday’s Champions League quarter-finals.
Yoann Vissa rounds out a memorable afternoon for Thomas Frank’s men, when they took a more comical advantage defending Chelsea to drill fourth.
A third win in four games moves Brentford to 14th place and 11 points away from the relegation zone.