Albert Rusnák scored a first-half goal and Stefan Frei made one save in picking up his second clean sheet of the best-of-3, first-round MLS Cup series as the Seattle Sounders eliminated FC Dallas in the rubber match with a 1-0 victory on Friday night. Seattle, the No. 2 seed, will host defending champion and third-seeded Los Angeles FC in the Western Conference semifinals. LAFC swept the Vancouver Whitecaps in a first-round series.