Despite an even start, four goals in 19 first-half minutes condemned John Mousinho’s men to a seventh-straight defeat on the road.
The Blues boss had rested five of his players and West Brom gleefully took advantage, albeit Nicolas Schmid gifting them the opening two goals with handling errors.
Thomas Waddingham came off the bench and marked his debut with a goal deep in stoppage time for a rare moment of joy for those travelling supporters as it finished 5-1.
And here are our Pompey player ratings...
6 / 6