The Red Stars celebrate Sarah Woldmoe's second-half goal against the Portland Thorns. (Craig Mitchelldyer/ISI Photos/Getty Images)

The way the NWSL semifinals unfolded on Sunday isn’t really how soccer games are supposed to go. League tables are generally a good indicator of a team’s quality and consistency, but the results of the day don’t always go the way of the technically better team. Sometimes winner-take-all tactics work, and the statistically unlikely outcome becomes reality.

This is why the NWSL playoffs are so exciting every year. The knockout bracket is its own brand of soccer, where teams might start off hesitantly but games often open up once goals are scored. The 90-minute clock begins to take on more urgency, players make uncharacteristic mistakes and, sometimes, the underdog walks out with the win.

On Sunday, the underdog Washington Spirit and the Chicago Red Stars never gave up when faced with climbing adversity. They stuck to their game plans, defeated their higher-seeded opponents and will now meet on Saturday in a championship matchup that nobody saw coming.

On one side, the challenges the Spirit have faced off the field this year are well-documented. The club fired coach Richie Burke in August after multiple players accused him of abusive behavior, a COVID-19 outbreak in September forced them to forfeit two key games and co-owners Steve Baldwin and Y. Michele Kang remain in an open dispute. Some of these wounds were self-inflicted, and some of them were completely outside of the players’ control.

On Sunday, adverse weather conditions affected both the Spirit and hosts OL Reign. Days of rain soaked the field at Cheney Stadium, adding another obstacle to the already narrow and somewhat short converted baseball field.

The Reign’s familiarity with the field would seem to make the conditions work in their favor, but the limited space also meant the other team’s defense could more easily clamp down on their high-flying attack. That didn’t stop the Reign from scoring the earliest goal in NWSL postseason history in the third minute, when Megan Rapinoe sent a beautiful ball in to a racing Eugénie Le Sommer, who shrugged off her mark and tapped it in.

That was the last time the Reign found the back of the net, despite out-shooting Washington 23 to 13. The Spirit adjusted to the moment, putting in shifts of last-ditch defending that held the Reign to just three shots on goal. The old adage that defense wins championships seemed to hold true in Tacoma on Sunday, but more specifically for the Spirit, defense kept them in the game so that the offense could then take its chances.

Washington’s first goal was a classic example of long-ball transition. Sam Staab lofted a ball over the top to a surging Trinity Rodman for the score and the start of another fantastic performance in her rookie campaign. Their second goal was even more audacious, with Ashley Sanchez taking the ball to the end line and finessing it over the head of Reign keeper Sarah Bouhaddi to put the Spirit ahead 2-1.

As they showed Sunday, the Spirit are operating at an intersection of high-level talent and youthful freedom that makes them difficult to defend simply because teams don’t know what they are going to try next.

Based on each team’s attacking data, the Spirit’s likelihood of winning that game was 5 percent. They overcame the in-game odds and pulled off a stunner, only to be one-upped a few hours later.

What the Chicago Red Stars achieved at Providence Park in the second semifinal of the day could be considered the greatest NWSL postseason upset of all time. This was Chicago’s first trip back to Portland since a 5-0 loss to the Thorns at the beginning of the season.

It was also their first game against Portland since a 2-1 victory in September that set the blueprint for the team Chicago became in the latter half of the season. The Red Stars prioritize organization without the ball, allowing their opponents to possess the ball but neutralizing all available attacking options. The resolve the Red Stars showed at the beginning of the match Sunday, starting Danny Colaprico in place of star striker Mallory Pugh (who missed the match due to COVID-19 protocol), was an early sign that the Thorns weren’t going to get the space they did back in May to put Chicago’s defense on its heels.

The Red Stars defended on every line — starting with their attack — and frequently collapsed in to get numbers in front of the ball. That part of the game-plan was clear from the first whistle. More unclear was how they would score without the individual magic of Pugh or Kealia Watt, who had to leave the match around the half-hour mark with an injury.

Chicago has been sneakily good at figuring out when to send numbers forward in transition, but the two goals they actually scored against Portland were highly unlikely conversions. Katie Johnson (who had subbed on for Watt) took a shot near-post on a tight angle in the 37th minute, one that Portland keeper Bella Bixby would usually be able to punch out for a corner kick, at worst. Bixby, however, didn’t have quite the right angle to stop the ball from sneaking into the back of the net, and suddenly the upset campaign was on.

While goals have sometimes felt like minor miracles for Chicago (who once relied on five-straight own goals to carry their offense), the Red Stars are almost impossible to play when they have a lead. Not many teams have the mental fortitude to defend for 60 minutes straight, and it’s frequently a losing tactic for groups with less experience. But the Red Stars live and breathe the defensive formation at this point in the year. And while Sarah Woldmoe scoring an even more improbable goal in the 59th minute added to a feeling of destiny, the Red Stars’ clean sheet was by design, and the Thorns had no answer.

The Red Stars scored two goals with an attack that generated exactly one-eighth of the game’s chances. The Spirit won a game they had a 5-percent chance of winning. And just like that, for the first time in NWSL history, the No. 3 and No. 4 seeds will be playing one another in the final, with each team looking to end their Cinderella stories with the first trophy in their club’s histories.

Their journeys to Louisville might have been improbable, but the Spirit and the Red Stars are exactly where they want to be.

Claire Watkins is a contributing writer at Just Women’s Sports covering soccer and the NWSL. Follow her on Twitter @ScoutRipley.