Substitute Jason Koumas struck a breakaway, last-gasp winner as West Brom claimed a crucial win at promotion rivals Sunderland to take a massive step towards a return to top-flight football.

Albion are now two points adrift of leaders Norwich in the Nationwide Division One title race but 12 points clear of third-placed Sunderland, who desperately needed a win to keep alive their hopes of a top-two finish.

The Black Cats failed to register a genuine attempt on goal until after half-time, and although the hosts offered a more purposeful approach in the second period, West Brom resolutely held firm, and Koumas' cool finish broke Sunderland hearts in the dying seconds.

Sunderland suffered an early injury blow when captain George McCartney - who was making a return after two games out with a sprained ankle - left the field on a stretcher to be replaced by Joachim Bjorklund following a crunching challenge from Andy Johnson with just five minutes on the clock.

Both sides struggled to retain possession in the opening stages with fierce tackling in midfield stifling the build-up play.

West Brom midfielder Sean Gregan made a vital interception to head clear Phil Babb's brilliant outswinging cross from the left flank.

Then Baggies defender Darren Moore survived a handball penalty appeal when he blocked Gary Breen's cross from the right.

The afternoon turned sour for Moore moments later though, as he limped off after pulling up under no pressure, with Koumas coming on to replace him.

Scott Dobie missed a glorious chance to open the scoring when he beat the offside trap to latch on to Mark Kinsella's through-ball.

Dobie, who has notched just four league goals all season, hesitated as he lined up his shot, and then blasted a right-footed effort over the crossbar from 15 yards.

Sunderland could have taken the lead within two minutes of the restart when they finally registered their first attempt on goal of the afternoon.

Albion goalkeeper Russell Hoult made a hash of punching clear Babb's cross, but Carl Robinson mistimed his effort from 10 yards and the ball looped harmlessly over.

The visitors made a change when striker Geoff Horsfield was replaced by Rob Hulse, and then Sunderland introduced Kevin Kyle in place of John Oster as Mick McCarthy looked to give his team an extra forward option.

Kyle missed a couple of decent openings, and then Babb headed straight at Hoult from six yards, as the home side continued to press.

However in the second minute of stoppage time West Brom struck a knockout punch, as substitute Lloyd Dyer raced out of defence, exchanged a one-two with Hulse, and played in the unmarked Koumas, who slotted home the winner with a calm right-footed finish from 10 yards.