Damien Duff lit up a gloomy night at The Hawthorns with a clinical piece of finishing to send Blackburn off on their UEFA Cup adventure in style.
But Rovers' delight was tempered when Dwight Yorke - who had come off the bench at half-time to put them ahead from the spot - limped off five minutes from time.
The former Manchester United striker had only just come back after a hamstring injury and this latest setback puts his appearance on Thursday night in Sofia in grave doubt.
Duff's finish at least gave the home crowd something to remember. The Republic of Ireland international was put clear by Yorke in the 76th minute and coolly rounded keeper Russell Hoult before making sure of the three points for Souness' men.
Yorke had given them the lead only five minutes earlier in rather controversial circumstances. Ronnie Wallwork pulled back Duff and although television replays suggested the initial contact was outside the Albion box the referee pointed to the spot and Yorke name no mistake with his lofted spot-kick.