Two-time MLS Cup champions in the past four years, the Seattle Sounders scored three goals in the final 18-plus minutes and beat Minnesota United 3-2 Monday night.
The Loons' 2-0 lead off the dominant left foot of Emanuel Reynoso in the first 66 minutes vanished in those final minutes when the Sounders scored three times, including Gustav Svensson's winner in the third minute of second-half stoppage.
The Loons scored the game's first two goals in the first 66 minutes and Seattle scored two more in the next 24, tying the score on star striker Raul Ruidiaz's short-distance shot off a corner kick in that 89th minute.
The Sounders will play for their third MLS Cup since 2016 at Columbus on Saturday night.
The Loons' loss ended their club-record unbeaten streak at 10 games including the regular season and playoffs.
Seattle still hasn't lost a home playoff game since November 2013.
The Loons hadn't beaten Seattle in six previous games. The Sounders were 5-0-1 lifetime against them, including 3-0 at home.
Make that seven games now.
Reynoso's dominant left-foot produced his team's first two goals, both on sweeping free kicks.
He scored the game's first goal — and his first MLS playoff goal — with a direct free kick from 35 yards away in the 29th minuite that was bend beautifully past Sounders keeper Stefan Frei.
Until then, Reynoso had three assists in his first two postseason games, 10 assists overall in his past five games and one goal, which came in a 3-0 regular-season finale victory over FC Dallas.
He did it in the 66th minute again, this time sending the free kick from the left side toward goal. This time, French defender Bakaye Dibassy flicked-on a header that beat Seattle goalkeeper Stefan Frei, just four days after he scored in Thursday's 3-0 victory at Sporting Kansas City with another header off another Reynoso kick, this one from the left corner.
It was also the 13th time in the Loons' last 14 goals on which Reynoso either assisted or scored.
Reynoso's seven postseason assists — in just three games — are the most in MLS, one more than Columbus' Guillermo Barros Schelotto's six in four matches and Chicago's Ante Razov six in seven matches in 2000.
Dibassy's goal came just moment after Sounders star Jordan Morris' clanked a powerful strike off the goal post from 20 yards away.
Seattle's Will Bruin brought his team within 2-1 in the 75th minute after a Seattle shot hit Loons defender Michael Boxall in the backside and Bruin promptly directed it past young Loons goalkeeper Dayne St. Clair.
Bruin's goal ended a Minnesota United club-record shutdown streak at 373 minutes, dating to a game against Chicago in the regular season's second-to-last game.
It also was a goal that created a frantic, final 15-plus minutes.
Reynoso's scoring free kick was created when Seattle defender Shane O'Neill received a yellow card for a sliding tackle into Loons veteran midfielder Ethan Finlay's ankle well outside the 18-yard penalty box.
The tackle was reviewed for a possible red-card infraction, but the yellow card stood instead, setting up Reynoso's bend, beautiful kick over the Seattle wall.
Sounders striker Raul Ruidiaz's apparent tying goal in the 53rd minute was overturned when a video review determined he committed a foul in a chase with Boxall. The review concluded Ruidiaz had knocked down Boxall with shoulder and arm before he continued on and scored with a running shot that Loons defender Hassani Dotson couldn't prevent.
The Loons lost starting right back Romain Metanire in the 38th minute after he went down on the fields— not once, but twice — while clutching his left leg each time.
He was helped off the field by the team's athletic training staff, one on each side as he limped heavily off.
Heath sent versatile midfielder Hassani Dotson into the game to play that right-back spot back home in the city where Dotson was raised in the Seattle suburb of Federal Way.