Chelsea were left stunned by Brentford after they were thrashed by their west London rivals at Stamford Bridge, with Christian Eriksen on target.
Antonio Rudiger had opened the scoring with a long range strike at the start of the second half, but Thomas Tuchel's side were immediately pegged back by a Vitaly Janelt equaliser.
Eriksen then turned the game around to give the Bees the lead, before Janelt struck again and Yoane Wissa added a fourth to complete an extraordinary comeback and give Thomas Frank's side a huge boost towards securing Premier League safety.