The Seattle Sounders take on FC Dallas as Major League Soccer's unusual 'best of three' format for the first round of the playoffs comes to a climax this weekend.

MLS's decision to adopt a limited version of the NBA and Major League Baseball's playoff format has had a mixed reception but the trio of 'Game Three' clashes have a more familiar feel.

"It's do or die," said Sounders defender Jackson Ragen, whose team was forced to a third match after a 3-1 loss at Dallas on Saturday following a 2-0 home win in the Western Conference series opener.

Aggregate scores are not a factor in this format, with each game decided by a penalty shootout if there is no winner after 90 minutes.

The Sounders, two-times MLS champions, finished second in the Western Conference regular-season standings and start as favorites against a Dallas team that was seventh.

But Ragen says the pressure of a big home crowd expecting victory and the prospect of a one-game clash at home to champions Los Angeles FC, isn't going to faze the team.

"I think there has been pressure on us in a lot of big games this year already, so we’re not trying to make too big a deal out of it, but we know in the back of our minds it's a big game," he said.

Head coach Brian Schmetzer, who guided Seattle to both their MLS titles, along with two other MLS Cup final appearances and a 2022 CONCACAF Champions League triumph, wants to see his team takes the game to Dallas.

"We've got to make sure that without exposing ourselves, that we come out on the front foot, play the way we want to play, dictate tempo, up tempo, good transition moments," he said.

Expectations

Schmetzer and his team are well used to the expectations that surround big knockout games, as midfielder Cristian Roldan noted.

"The experience that we have on our team is unheard of, right?" Roldan said.

"Going through Champions League, being in MLS Cup finals, four of them -– we're experienced. I think that's going to play a huge part, especially at home against a young Dallas team. (But) it's not going to be easy."

Dallas suffered a major blow with the loss of Argentine midfielder Alan Velasco to a knee ligament injury in Saturday's win.

The Texas side have a poor record in Seattle, having one just once in 21 games away to the Sounders -- and never in the playoffs.

If they are to pull of a surprise and progress to the conference semi-finals, they will need winger Bernard Kamungo to deliver another impactful display.

Kamungo was born in Tanzania and lived in a refugee camp before moving to the United States as a 14-year-old and has been one of the brightest stars for Dallas this season.

Already tipped to be one of the increasing flow of MLS players heading to Europe, he says he is determined to taste success with Dallas first.

"This club has been amazing to me this whole time. It just trusted in me and gave me the opportunity to showcase my talents. And just to represent this whole community is just such a dream," Kamungo said.

"Before I leave, I want to make sure I do something great for this club."

The Houston Dynamo have already picked up one piece of silverware this season, having beaten Inter Miami in the final of the US Open Cup, and Ben Olsen's squad look to continue the search for another trophy when they host Real Salt Lake on Saturday.

The winner of that game will play Sporting Kansas City, who upset Western Conference top seed St. Louis City in two games.

The first round concludes on Sunday with Columbus Crew hosting Atlanta United with a matchup against Orlando City for the winner.