In an afternoon, Minnesota United slid from second place in the Western Conference to fourth place after a 1-0 loss at Seattle last Sunday, also known as MLS Decision Day.

The Loons still earned a first-round home playoff game Oct. 20 against L.A. Galaxy but now must travel a shorter but arguably tougher road than they would have in previous years. This season’s new format, designed to reward regular-season record and home-field advantage, makes every playoff game a knockout game.

Gone is the two-game, home-and-home series determined by aggregate goals. The way to next month’s MLS Cup final is two games shorter because of that — three instead of five — but United very likely will have to win two games away from Allianz Field to get there.

“It can be done,” United veteran midfielder Lawrence Olum said.

He knows. He has been there.

Olum’s Portland team entered last season’s playoffs seeded fifth in the West. The Timbers won three road games — and a pivotal penalty-kick shootout in a fourth — to reach the MLS Cup, where they lost 2-0 at Atlanta.

“The first job is to get in, and we have,” Olum said. “We would want a better seeding, but it’s the belief the guys have. I think this team does believe we can get through and go to the final game.”

Portland won at fourth-seeded Dallas in a first-round knockout game on Diego Valeri’s two consecutive goals, the second coming with the Timbers playing down a man. Next was a two-game, second-round series with Seattle. Portland won 2-1 at home and lost 3-2 at Seattle, then won the series 4-2 on penalty kicks after two games ended tied in total goals.

Then Portland won a second-half shootout 3-2 at Kansas City, the second of a two-game Western Conference final series that started with a scoreless first game. Valeri scored twice in that second game as well.

“We got a roll,” Olum said. “The guys believed we could do it. We won two games on the road [and the penalty-kick shootout in Seattle] to get to the final. It’s the same this team has: We have to win the first game at home and at least two on the road to get us there.”

The new playoff format is intended to make the regular season more important by eliminating the chance for every playoff qualifier to play at least one game at home. But Olum disagrees that win-or-done gives the home team a lopsided advantage, even though regular-season records show otherwise.

“Actually, there is more pressure on the home team because they have to come out and make the game,” Olum said.

United coach Adrian Heath, however, looks at MLS standings and will play the odds in a league where his team went 10-1-6 at Allianz Field and 5-10-2 away from it. The Galaxy went 11-5-1 at home and 5-10-2 as well on the road.

“Playing at home, you only have to look at the league table,” Heath said. “Most teams in the league predominantly pick up their points at home. The fact you don’t travel, the fact you’re at home, it’s a big, big advantage for them teams. But we all knew what the rules were before. I could say that if we wanted home games, we should have finished higher up the table.

“We had an opportunity to do that this weekend. So that was up to us.”

Then again, in a one-game knockout anything can happen.

“Once you get to this stage, if you play well in a couple games and you get some confidence,” Heath said. “And you get a bit of luck, which you all need along the way. LAFC was in the same position this time last year and got beat by Real Salt Lake [in an opening knockout round]. Nobody saw that coming. But that’s football for you. That’s sport. Two teams on a given day, you may be an injury away or a poor referee indecision from the game turning it on its head.

“All we can do is prepare the best we can and hope we play with the drive, the enthusiasm and the determination that we expect from them. If we do, we’ll take what comes.”