The Union’s unprecedented MLS playoff run will continue Sunday when they host New York City FC in the Eastern Conference final at Subaru Park (3 p.m., 6abc and ESPN Deportes). It’s the first time in the Union’s 12-year history that they’ve advanced this far in the postseason.

Ahead of Sunday, here’s a look back at 11 key games this year — a starting lineup’s worth — that paved the way for the Union to reach this point.

» READ MORE: A first look at the Union-NYCFC matchup

April 7: A 1-0 win at Saprissa

This was the Union’s first game of the year, and the start of their inaugural foray in the Concacaf Champions League. It was also the first game since Brenden Aaronson and Mark McKenzie moved to European clubs and Ray Gaddis retired. And it was on the road in Costa Rica.

A first-half goal from Kacper Przybylko and a lot of defending afterward — including from 17-year-old Quinn Sullivan in his first-team debut — helped seal a 1-0 win. It helped that the stands were empty at Saprissa’s famous old bandbox. But the home team had plenty of veteran players, and the Union were able to keep their heads amid a bench-clearing brawl at the end.

A week later, the Union won the second leg in Chester in a stunning 4-0 rout. That provided a huge boost of confidence heading into their MLS opener four days after that.

» READ MORE: Union win Concacaf Champions League debut, 1-0 over Saprissa, on Kacper Przybylko goal

April 27: A 3-0 win at Atlanta

If beating Saprissa by that much was a surprise, this was a shock. The Union kicked off the Champions League quarterfinals with a stomping of one of MLS’ flagship teams on its own turf. All three goals came in the second half, the first two from Przybylko and the third from Anthony Fontana via a Przybylko assist.

The margin was so vast that the 1-1 score in the second game in Chester was promptly forgotten. But the trash talk afterward between Jim Curtin and then-Atlanta manager Gabriel Heinze after both games sure wasn’t.

» READ MORE: Union’s Jim Curtin gets another win over his critics, including Atlanta United’s Gabriel Heinze

May 30: A 3-0 home win over Portland

The Union snapped a six-year losing streak to another of MLS’s benchmark teams with a nationally televised rout. Przybylko, Sergio Santos, and Jack Elliott scored, putting the game so far out of reach that fans chanted for Paxten Aaronson to make his MLS debut. They got their wish right at the end.

» READ MORE: Why Paxten Aaronson’s Union debut was no fluke

June 20: A 2-2 tie at Atlanta

As MLS returned from a three-week break for national team tournaments worldwide, the Union and Atlanta met for the first time since the Champions League series.

Atlanta went up 2-0 in the 83rd minute, but the Union charged back with a Cory Burke goal a minute later and one of Jakob Glesnes’ trademark thunderbolts in the 93rd. The equalizer sent Jim Curtin sprinting down the sideline in celebration, just as he would when Glesnes’ magic won the Union’s playoff opener five months later.

» READ MORE: Jakob Glesnes has the green light to attack. He went into overdrive to score an epic goal.

Aug. 8: A 2-1 loss at New England

With the Champions League semifinals set to start four days later, Curtin effectively punted this game by starting a bunch of backups. And while it offends Philadelphia tradition to not go hell-for-leather in every game, Curtin was widely praised by Union fans for doing the right thing against the eventual Supporters’ Shield winners. The team looked decent, too, including Aaronson’s first MLS goal.

» READ MORE: Union lose 2-1 at New England Revolution: Observations and analysis

Sept. 15: A 2-0 home loss to Club América

Even with the playoff run, this remains the biggest game in Union history. Subaru Park was electric, bipartisan and bilingual for the visit of Mexico’s biggest club in the Champions League semifinals.

The Union gave it everything they had, knowing an early goal would cut the 2-0 aggregate deficit they faced in half after the first game at fabled Estadio Azteca. But it wasn’t to be, as Mexico’s biggest club held the challengers off and scored two more goals late to finish things.

In the end, everyone left the night with their heads held high. América manager Santiago Solari, who played a year of college soccer at Stockton near the Jersey Shore, was full of praise for Curtin and his players. Hopefully, the generations of América fans from the Philly area who went to the game liked what they saw, and hopefully, the Union convinced them to make the local team an adopted favorite.

» READ MORE: Santiago Solari returned to the Philly area for the Concacaf Champions League, 27 years after starring at Stockton College

Sept. 19: A 3-1 home win over Orlando

For years, MLS teams that make Champions League runs have suffered hangovers when the runs end. But the Union didn’t. This was their first game after the América series, and it started a run of just one loss in 11 games to end the regular season.

» READ MORE: Union win 3-1 over Orlando City as Kacper Przybylko breaks long scoreless drought

Oct. 20: A 3-2 loss at Minnesota

This was the aforementioned one loss. Fortunately, the Union rebounded from it enough to ensure that the game was remembered more for Dániel Gazdag’s first two goals from open play with the team.

» READ MORE: Union lose to Minnesota United, 3-2, with surprisingly bad defense

Oct. 23: A 1-0 home win over Nashville

It put the Union in the driver’s seat to finish in second place, and they stayed there the rest of the way.

» READ MORE: Kacper Przybylko’s penalty kick powers Union over Nashville, 1-0

Nov. 20: A 1-0 win over the New York Red Bulls in extra time

When Andrew Gutman’s headed clearance fell to Glesnes in the 123rd minute, Glesnes had never taken a penalty kick in his career. What happened next helped ensure he still hasn’t.

Of the three thunderbolts the Norwegian center back has scored for the Union, that one had the highest degree of difficulty. It wasn’t just a smash; it was a curling, dipping strike that went up over the outstretched left leg of New York midfielder Youba Diarra and down over goalkeeper Carlos Miguel Coronel into the net.

In a dozen years of games at Subaru Park, there had never been an explosion of noise quite like that.

» READ MORE: Jakob Glesnes’ epic game-winning goal set off one of the Union’s all-time celebrations

Nov. 28: A 2-0 penalty shootout win over Nashville after a 1-1 tie

Despite the drama of the first-round playoff game, this was the one that really made history.

With Subaru Park as loud as it’s ever been, the Union’s first-ever second-round home playoff game lived up to the billing. Nashville’s MVP candidate Hany Mukhtar opened the scoring, and Gazdag answered him just before halftime.

In the shootout, Andre Blake saved the visitors’ first two shots to set the tone. Then Jack McGlynn showed his 18-year-old veins are packed with ice, and Nashville star defender Walker Zimmerman missed to end it.

» READ MORE: Jack McGlynn was the Union’s penalty kick sensation

» Join The Inquirer’s soccer staff for live coverage of the Union’s Eastern Conference final showdown with New York City FC on Sunday in Union Gameday Central. Kickoff is set for just after 3 p.m.