TUKWILA, Wash. >> For the second straight season, the Seattle Sounders will begin the MLS Cup playoffs with Clint Dempsey as a spectator.

Unlike last year’s championship run by the Sounders, this absence by Dempsey will last only one game.

Dempsey was suspended for Sunday’s first-leg of the Western Conference semifinals against Cascadia rival Vancouver after picking up a red card in the regular-season finale against Colorado. Dempsey was sent off early in the first half of Seattle’s 3-0 victory last week that clinched the No. 2 seed in the West for the defending champs.

“We are no longer the underdog,” Seattle midfielder Cristian Roldan said. “We’ve accepted that. We’ve felt that way throughout the season because of MLS Cup and being champions. It’s a big deal and teams are gunning for you.”

The other semifinal matchup in the West features No. 1 seed Portland facing Houston. In the East, Supporters’ Shield winners Toronto FC will face the New York Red Bulls, while No. 2 seed New York City FC will take on Columbus. Both the conference semifinals and finals are decided by two-game aggregate scoring.

The loss of Dempsey for the first-leg against the Whitecaps is amplified for Seattle because of the uncertainty surrounding forward Jordan Morris, who has been out since early September with a hamstring injury. Morris has been doing work on the side, but has yet to resume full training.

Vancouver did have success at home this season against Seattle, winning in April and taking a 1-1 draw in August. But the Whitecaps were routed 3-0 in Seattle in late September. Vancouver lost three of its final five regular-season matches prior to Wednesday’s 5-0 rout of San Jose in the knockout round.

Here’s a look at the three other conference semifinal matchups:

EASTERN CONFERENCE

Toronto FC (1) vs. New York Red Bulls (6)

>> First leg: Monday, Oct. 30, Red Bull Arena

>> Second leg: Sunday, Nov. 5, BMO Field

Toronto was clearly the class of MLS this season, running away with the Supporters’ Shield in dominating fashion. Toronto took the disappointment of losing to Seattle in last year’s title match and posted the highest point total in league history, finishing the season with 69 points and 20 victories in 34 matches.

The Reds stumbled in late September with consecutive losses to Montreal and New England — both of which missed the playoffs — but recovered with victories in two of their final three matches, including a 4-2 win over the Red Bulls on Sept. 30.

The loss to Toronto was the last time New York stumbled. The Red Bulls won two of their final three to close the regular season then routed Chicago 4-0 in the knockout round on Wednesday.

The Red Bulls have fans on every Western Conference team. The only way a team from the West can host MLS Cup is if the Red Bulls advance to the final.

New York City FC (2) vs. Columbus Crew (5)

>> First leg: Tuesday, Oct. 31, Mapfre Stadium

>> Second leg: Sunday, Nov. 5, Yankee Stadium

Led by David Villa and emerging youngster Jack Harrison, NYCFC posted its finest season with 57 points and a second-place finish in the East. Villa finished the year with 22 goals and likely will be in the middle of the MVP discussion. But the big difference for NYCFC was its improved defense that allowed 14 fewer goals than last season.

Columbus rode the goalkeeping of Zack Steffen to oust the expansion Atlanta United on penalties in the knockout round. The stunning victory continued the Crew’s surge to close out the season. Columbus is now unbeaten in 11 straight matches dating to Aug. 5.

Columbus and NYCFC played to a 2-2 draw in the regular-season finale in New York.

WESTERN CONFERENCE

Portland (1) vs. Houston (4)

>> First leg: Monday, Oct. 30, BBVA Compass Stadium

>> Second leg: Sunday, Nov. 5, Providence Park

Portland earned the top seed in the West thanks to a 2-1 win over Vancouver in the regular-season finale, capping a six-week run where the Timbers won four of six matches to claim the top spot. Portland has been led all season by MVP-worthy Diego Valeri, who has 21 goals and 11 assists. Key for Portland will be the health of striker Fanendo Adi, who missed the final two months of the regular season with a hamstring injury.

Houston outlasted Sporting Kansas City 1-0 in extra time in the knockout round. The Dynamo are in the playoffs for the first time since 2013, led by Alberth Elis, Erick Torres, Mauro Manotas and Romell Quioto, who combined for 41 of 57 goals in the regular season. But the Dynamo suffered a big setback losing defender A.J. DeLaGarza in the regular-season finale to a knee injury.

The Timbers beat the Dynamo in Portland early in the season and pulled out a 2-2 draw in their match in Houston in July.