SEATTLE - Nelson Valdez subbed on late in the match, then scored his first MLS goal in 2016 at just the right time. Valdez headed in a cross from Joevin Jones in the 88th minute, and the Sounders beat Sporting KC 1-0.
Sounders keeper Stefan Frei was outstanding, staving off seven shots.
Seattle now moves on to face FC Dallas in the Conference Semifinals. The first leg of the two-match aggregate series is Sunday at CenturyLink field at 6:30 p.m. PT.
This will mark the third straight year Seattle and Dallas will meet in the playoffs. The Sounders won it 2014, while Dallas knocked Seattle out in 2015.