The Union lost 2-1 at the New England Revolution on Sunday. But the result was less important than how the Union played. Here’s why.

Starters sit

It’s a compliment to Union fans that there was strong agreement with the suggestion from here that Jim Curtin should rest as many starters as possible in this game, so they can be in the best shape for Thursday’s Concacaf Champions League semifinal at Club América (10 p.m., FS1 and TUDN).

Curtin didn’t need public backing to do the right thing, but it was nice to have. And he sure did it.

Alejandro Bedoya came off the bench for the first time since Sept. 23, 2018, and just the third time in his five seasons with the Union. Kacper Przybylko, Dániel Gazdag, and Kai Wagner were also on the bench. Cory Burke didn’t even travel.

In their places were Paxten Aaronson, Quinn Sullivan, Jack McGlynn, and Stuart Findlay.

Did those moves cost the Union (7-5-7, 28 points) a chance to win against the Eastern Conference’s best team? It turned out they didn’t. The youngsters brought an energetic spark to an open game, and showed they deserve more playing time down the road.

“I thought that our young players stepped out on the field and showed that they more than belonged, which was great to see,” Curtin said.

The Union won’t be favored on Thursday at Club América, the biggest and richest team in North America. They’re Mexico’s version of the Cowboys and Yankees, and the Estadio Azteca is every bit as famous as Yankee Stadium: 87,000 seats (though they won’t all be full) at 7,200-foot altitude.

It will take big changes to MLS’ Byzantine roster rule book before the league’s teams are ever favored on a regular basis against Mexican clubs that have more talent, more depth, and a whole lot more money. But Curtin’s willingness to punt this game gives his team the best chance for a positive result in Mexico. That’s what matters most.

Formation change

Along with changing the lineup, Curtin changed the formation. It wasn’t the first time the team has played a 3-4-3, but it was the first time anyone could remember starting that way.

Stuart Findlay looked pretty good playing left center back next to Jack Elliott, with Jakob Glesnes to Elliott’s right. Leon Flach started on the left side of the midfield four, with McGlynn and Jose Andrés Martínez in the middle and Olivier Mbaizo on the right. The front three was Aaronson, Sergio Santos — in a rare appearance as a lone striker — and Sullivan.

Curtin stuck with the formation even as he made many substitutions in the second half: Przybylko for Santos, Wagner for Flach, Bedoya for Martínez, Ilsinho for Mbaizo, and Gazdag for Sullivan.

“We trained it, I’d say, two and a half days and gave the guys some basic ideas and some basic principles, and they really took the information well,” Curtin said. “There’s still little things we can improve, but it certainly gives us now something in the back pocket. … We learned a little bit more about our group.”

Indeed we did. The execution wasn’t perfect, but it was good enough — and pretty entertaining. It’s also another sign of Curtin’s tactical flexibility under sporting director Ernst Tanner. We’ve now seen this team play four different formations in the last year and a half. That’s a very good thing.

» READ MORE: Quinn Sullivan’s bicycle-kick goal in his first MLS start was a dream moment for one of Philly soccer’s most famous families

Aaronson’s first MLS goal

What will really be remembered from this game is Aaronson’s first MLS goal, a belted shot from the top of the 18-yard box after he dribbled past through three New England (12-3-4, 40 points) defenders. It came in his first MLS start, and four days after his first substantial minutes in a MLS game.

The play will certainly be remembered far longer than either New England goal, Matt Polster’s 10th-minute opener or Gustavo Bou’s 39th-minute putback of his penalty kick that Andre Blake saved.

Scouts and observers who’ve watched Brenden’s younger brother rise from the Union academy to the pros have been readying the hype train for a while now. The 17-year-old from Medford still has plenty of growing to do, but that goal was the all-aboard warning.

» READ MORE: Paxten Aaronson could hvae a higher ceiling than Brenden