Defending champion Seattle Sounders continued their impressive march through another postseason on Tuesday, while Nashville SC and the New England Revolution scored upsets in a pair of Eastern Conference playoff clashes.

Raul Ruidiaz delivered a goal and two assists as the Sounders advanced with a 3-1 victory against the shorthanded Los Angeles FC on a rainy evening in the Pacific Northwest.

Ruidiaz, of Peru, has eight goals and six assists in seven career North American Major League Soccer postseason games.

Nicolas Lodeiro and Jordan Morris each added a goal and an assist as the second-seeded Sounders reached the Western Conference semi-finals where they will face FC Dallas.

Seattle goalkeeper Stefan Frei stopped a penalty shot by Carlos Vela who returned Tuesday from an injury.

LAFC were missing four starters, including Diego Rossi, of Uruguay. The MLS Golden Boot winner and MVP finalist Rossi, Brian Rodriguez (Uruguay), Jose Cifuentes (Ecuador) and Diego Palacios (Ecuador) travelled to South America for World Cup qualifying earlier this month and all four tested positive for the coronavirus.

Because of their depleted roster, LAFC were forced to give a bigger role to 16-year-old rookie Christian Torres, who spent last season in the club's academy program.

Eduard Atuesta scored the only goal for LAFC in the loss.

Meanwhile, Tajon Buchanan scored a first half goal and Carles Gil delivered two assists as visiting New England Revolution shocked top seeded Philadelphia Union 2-0.

Adam Buksa also scored for the Revolution who beat Philadelphia for the first time in six tries this season to reach the league quarter-finals where they will face fourth seeded Orlando City on Sunday.

"We knew we had a fighting chance to beat them. We are happy to do that," said Canadian Buchanan.

He scored in the 30th minute to give the Revolution a 2-0 lead. The ninth overall pick in the 2019 draft dribbled in alone and beat goalkeeper Andre Blake with a right-footed shot.

"I just wanted to go at him one on one," said Buchanan. "I am happy it went in the back of the net. I try to bring fight and energy to these games."

This was also the first loss of the season at home for Philadelphia who captured the Supporters' Shield as the league's top regular-season team for the first time in franchise history.

Blake, the MLS goalkeeper of the year, was playing his first game since suffering a broken hand.

The eighth seeded Revolution have now won two straight playoff games after beating the Montreal Impact 2-1 on Friday.

Also, Daniel Rios' goal in extra time gave seventh seeded Nashville SC a 1-0 victory over host Toronto FC in East Hartford, Connecticut.

In the 108th minute of play, Hany Mukhtar made a nice move to get open in a crowd and to blast a shot. Goalkeeper Quentin Westberg made the save, but Rios was there for the easy tap-in goal.

Nashville, who are in their first season of existence, advance to visit the third-seeded Columbus Crew in the next round on Sunday.