The visitors, led by Chicharito, were the talk of the league through the first two weeks, with the Mexican striker scoring five times in two wins.
But the Sounders quickly reminded the Galaxy who the defending conference champions are. Raul Ruidiaz scored in the 20th minute off a pass from Brad Smith. Three minutes later, Smith scored for a 2-0 lead on a cross by Cristian Roldan.
Ruidiaz capped the win with a brace as he scored in the 93rd minute to put the game on ice. Nicolas Lodeiro made his 2021 debut, coming on as a substitute in the 66th minute in his return from a preseason injury.
With the win, the Sounders now have seven points, most in the West. The Galaxy suffered their first loss of the season and were shut out in the process.
Both teams now get ready for rivalry games next weekend. The Sounders face Portland Timbers in the Cascadia Cup. PaddyPower has Portland at 24/13 with Seattle at 33/20 and a draw at 11/4.
Meanwhile, the Galaxy face LAFC in El Trafico. The Galaxy are 24/11 with PaddyPower, LAFC at 5/4 and a draw at 14/5.
Nani leads Orlando SC to win
Orlando City SC picked up their fastest-ever goal and cruised to a 3-0 win over FC Cincinnati on Saturday night. Tesho Akindele scored just 33 seconds after the opening kickoff, breaking the team record by 30 seconds.
In the 19th minute, Nani scored to double the lead. His left-footed shot put the Lions on top 2-0. The former Manchester United winger nearly scored with a header minutes later, but his attempt was deflected off the post. He also had a shot saved by Przemyslaw Tyton early in the second half.
Orlando City made it 3-0 in the 80th minute as Junior Urso scored. The win is the first of the season for City, who will face NYCFC on Saturday in their next game. The Lions are 10/7 with Paddy Power, NYCFC at 7/4 and a draw at 3/1.
Jaap Stam's FC Cincinnati side are really struggling. They have allowed ten unanswered goals since scoring in the opener and have lost the last two games by a combined 8-0. They have this week off in the MLS scheduled before finally returning home to open brand new TQL Stadium on May 16 against Inter Miami CF.
Real Salt Lake stay perfect
Rubio Rubin scored twice as RSL overturned an early 1-0 deficit to knock off SKC at Rio Tinto Stadium. Damir Kreilach scored the opener in the first half on a cross from Andrew Brody.
Real Salt Lake will look to stay perfect on Friday as they play the San Jose Earthquakes. According to PaddyPower, RSL are 21/20, while San Jose are 27/11, and a draw is 26/9.
Meanwhile, Sporting KC will next face expansion side Austin FC on Sunday. The line is not yet available.