Despite that numerical disadvantage, Christian Pulisic put Chelsea ahead, but two goals from Costa Pereira — both in first-half stoppage time — ensured the visitors were ahead at halftime.
A brilliant volley from substitute Callum Robinson extended West Brom’s lead and then Mbaye Diagne’s fine finish added a fourth, before Mason Mount’s tap-in reduced the deficit.
That was the 59th goal in 30 games that West Brom have conceded in the league this season but the visitors didn’t panic and Robinson netted his second with a deft finish in the game’s final minutes.
The win keeps West Brom’s survival hopes alive and moves Sam Allardyce’s team onto 21 points, seven behind fourth from bottom Newcastle United.
“It’s an unbelievable day,” Robinson told BT Sport; “It’s been a tough season but it’s nice to come here and get so many goals and really enjoy it. It’s a good day all round.
More to follow.