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...
5. Connor Ogilvie - 8
Mousinho’s preference for a right and left-footed centre-half partnership saw him return to the position and it was another no-nonsense display. Magnificent in the air and rugged on the ground. Photo: Graham Hunt
6. Andre Dozzell - 8
Another powerhouse performance in the centre of midfield, capped by Pompey’s third goal, after capitalising on Chaplin’s pass. Now has his own song too as his instant impact continues. Photo: Graham Hunt
7. Ebou Adams - 8
(Replaced by John Swift on 84 mins) Another powerhouse performance in the centre of midfield, capped by Pompey’s third goal, after capitalising on Chaplin’s pass. Now has his own song too as his instant impact continues. Photo: Graham Hunt
8. Adrian Segecic - 8
(Replaced by Marlon Pack on 75 mins) A bright, lively first half, in particular. Almost got himself on the scoresheet when he diverted Devlin’s shot and brought a save out of O’Leary. Starting to develop a good understanding with Chaplin. Photo: Graham Hunt