Sunderland boosted their hopes of gaining automatic promotion to the Barclays Premiership with a crucial win at The Hawthorns as they moved level on points with Tony Mowbray's side.
First half goals from Dwight Yorke and Stern John extended the Black Cats unbeaten league run to 10 games from which they have collected 26 points.
They are now only three points behind leaders Derby and have a momentum under Roy Keane which suggests they will be difficult to stop between now and the end of the season.
Keane came up with the perfect tactics to stifle the normally free-flowing Baggies, defending with two solid banks of four - skipper Dean Whitehead was outstanding in midfield - and hitting the home side on the counter-attack.
Only in the final quarter did Albion gain any sort of momentum after Mowbray had made a triple substitution but Darren Carter's second strike in successive matches proved in vain as their eight-game unbeaten league run came to an end.
To add to their misery Albion defender Paul Robinson was sent off with three minutes remaining for a professional foul on David Connolly although there appeared to be no contact.
After 24 minutes the Black Cats went ahead through Yorke's fourth goal of the campaign.
Danny Simpson cut in from the right wing before playing the ball into the feet of John and his first time flick found Yorke who side-footed the ball past Dean Kiely into the corner of the net.
Albion defender Neil Clement and Sunderland skipper Whitehead were booked for fouls on Carlos Edwards and Robert Koren respectively.
Sunderland were forced to make a change after 40 minutes when Carlos Edwards picked up a serious looking shoulder injury after a challenge from Richard Chaplow and he was replaced by Tobias Hysen.
But five minutes into the second period Sunderland doubled their lead with John's third goal since his move from Coventry in January.
The Albion marking was non existent from an inswinging corner by Whitehead to leave John with a free header at the far post - and he made no mistake.
Darren Ward parried a fierce Chaplow drive and at the other end Kiely pulled off a similar stop to deny Hysen.
Mowbray made a triple substitution after 55 minutes, bringing on Zoltan Gera, Sherjill MacDonald and Darren Carter for Koren, Kevin Phillips and Jonathan Greening.
Koumas had a fierce drive gathered by Ward away to his left and Robinson's drive was deflected inches over the bar.
Then Carter gave Albion a life-line when he hooked the ball past Ward from the edge of the box after Jonny Evans had only half cleared with 18 minutes remaining.
But Connolly should have wrapped the points up only for Kiely to keep out his header at point blank range.
Then came the harsh red card for Robinson before Sunderland celebrated with their 2,600 travelling fans at the final whistle.