Galaxy edge win over Sounders
Mike Magee came off the bench in the 75th minute at the Home Depot Center and netted the game's only goal eight minutes later from a Robbie Keane assist.
The result saw Real Salt Lake finish second in the West. Seattle would have claimed second spot and the number two seeding by avoiding defeat against the defending champions.
Elsewhere, Chivas USA scored in the 90th and 94th minutes to salvage an unlikely 2-2 draw against FC Dallas.
Second-half strikes from Jackson and Fabian Castillo looked to have set the hosts on course for three points at FC Dallas Stadium.
But Laurent Courtois and Juan Agudelo had other ideas and grabbed late goals to ensure the spoils were shared in what was the season finale for both teams.
Federico Higuain's double ensured
The Argentinian opened the scoring in the 17th minute and then converted the decisive penalty in the 62nd minute after Andrew Wiedeman had equalised.