Diego Rossi scored a penalty kick early in the first half and provided the clinching goal in the 82nd minute.
LAFC advanced to the quarterfinals of the MLS is Back tournament by getting a measure of revenge for last year’s Western Conference final when Seattle pulled off a 3-1 upset in Los Angeles on its way to winning the league title.
Rossi was the leader of LAFC's buzzing attack. He scored twice and probably should have scored two or three more times. Arreaga’s foul in the penalty area and beat Seattle goalkeeper
Latif Blessing doubled the lead in the 39th minute when his shot toward the far post was deflected by Seattle defender Shane O’Neill and into the net. Frei appeared to be in position to make the save, but O’Neill shifted his shoulder and deflected the attempt.
Rossi provide the insurance goal after Seattle had cut the deficit to 2-1. He took advantage of another defensive mistake by Arreaga and regained the two-goal advantage. Rossi now has seven goals in the tournament. Brian Rodriguez added another goal in the 89th minute.
Seattle had four extra days of rest, but looked lethargic for most of the match. It took 65 minutes before the Sounders got a shot on LAFC goalkeeper Kenneth Vermeer.
But the Sounders managed to create a nervous final 20 minutes for LAFC. Substitute Will Bruin scored in the 75th minute for Seattle to cut the deficit to 2-1 in his first appearance in more than a year after a major knee injury.