Nelson Valdez came off the bench to lift Seattle Sounders to a dramatic 1-0 win over Sporting Kansas City in Thursday's MLS Western Conference knockout fixture.

Scores were deadlocked at 0-0 in Seattle until Valdez sparked pandemonium in the stands with his 88rd-minute header.

Valdez met Joevin Jones' cross, albeit contentiously as replays suggest a tight offside call, to net the winner - with the Paraguayan having gone 26 MLS matches without a goal.

The Sounders will now take on Supporters' Shield champions FC Dallas in the Western Conference semi-finals.

Didier Drogba was once again a notable absentee but Montreal Impact still surged past DC United 4-2 in their Eastern Conference elimination clash.

Yet to play since refusing to sit among the substitutes for Montreal's penultimate regular-season clash and battling a back problem, former Chelsea striker Drogba was nowhere to be seen in Washington.

However, it mattered little as the Impact crushed hosts DC in the American capital.

First-half goals from Laurent Ciman and Matteo Mancosu silenced the home faithful, before the latter and Ignacio Piatti put the result beyond doubt.

Lamar Neagle and Taylor Kemp salvaged some pride for DC - who finished a point above Montreal in the regular season - in stoppage time but there was no denying the Impact a semi-final showdown with New York Red Bulls.