Chelsea were down to 10 men for the most part of the game after Thiago Silva’s red card just moments after the Blues had taken the lead through Christian Pulisic in the first half.
But West Brom, fighting for their lives in the relegation battle played brilliant football against Chelsea in the Blues’ own backyard.
Two goals from Matheus Pereira flipped the game in first half stoppage time, before Callum Robinson made it 3-1 and Mbaye Diagne added the fourth goal for West Brom.
Mason Mount scored what proved to be a consolation goal to make it 4-2, and with 20 minutes left, Chelsea fans hoped their side could mount a comeback .
But the Blues were set for misery as Robinson scored again leaving the score at 5- 2 full time.
Chelsea remain fourth on the premier league table while West Brom will surely see this as fuel to help them battle relegation with barely a dozen games left this season.