Matt Real and Nathan Harriel are covering left back for the Union while Kai Wagner is hurt

It was a surprise to see right back Nathan Harriel start at left back in the Union’s game against Atlas on Tuesday. But maybe it shouldn’t have been.

Kai Wagner is out with a hamstring strain, and the Union had a short turnaround between games last Saturday and Tuesday. Matt Real hadn’t gone through that much as a pro, and academy product Anthony Sorenson isn’t ready for the big-time yet.

Harriel’s strong defensive acumen meant he could fit in the role for a day. And it wasn’t the first time he played there: he did it in the 2021 Eastern Conference final when COVID-19 protocols sidelined 11 Union players.

The 21-year-old doesn’t make as many swashbuckling attacking forays as Wagner, whose runs and crosses are a key part of the Union’s system. But there are ways to make up for that, and manager Jim Curtin picked one of the better ones on Tuesday.

If the 4-3-2-1 formation was unusual, putting Jack McGlynn on the left side of the line of three made lots of sense. Harriel backstopped things behind McGlynn, allowing the latter to craft one of the best games of his career.

» READ MORE: Jack McGlynn seized his chance to shine against Atlas in a too-rare start

“He’s a real one-v-one defender, and he did a great job against Atlas,” Union manager Jim Curtin said of Harriel. “And it shows if something did happen to Matt we can do that at any moment.”

For now, the starting job will return to Real when the Union visit FC Cincinnati on Saturday (7:30 p.m., Apple TV, paywalled), in the latest chapter of an increasingly spicy rivalry.

Wagner is on track to to return next Wednesday for the Champions League quarterfinal second leg game at Atlas (10 p.m., FS1, TUDN). He’s been working out on the sideline during practices this week.

“He’s progressing really, really well,” Curtin said. “Fortunately it doesn’t look like it’s going to be a long-term injury at all.”

But the Union now have another tool in the box, which is no bad thing. Many teams have grown accustomed to facing the Union’s traditional 4-4-2 diamond setup, and are figuring out how to stifle it.

» READ MORE: Mikael Uhre knows he and the team aren’t playing well enough

It’s been quite a week for the Union’s youth academy teams at the prestigious Generation adidas Cup in Bradenton, Fla. The club’s under-17 and under-15 teams are in their age groups’ semifinals after wins over some big teams from other countries.

The under-17 squad swept the Houston Dynamo, Minnesota United, and the Bradenton-based IMG Academy in the group stage, beat Nigeria’s Remo FC in the round of 16, then topped Brazil’s Palmeiras in the quarterfinals on Thursday.

Names to know include David Vazquez, a Los Angeles native who came to the Union’s academy this year as a big-time prospect. He also plays for the U.S. under-17 national team, and will likely be on the team’s World Cup squad later this year.

» READ MORE: From L.A. to Philly, David Vazquez’s Union Academy life could have gone a different direction

Two centerbacks on the squad have older siblings on the Union. Andrew Craig’s brother Brandan is also on the U.S. under-20 national team; Neil Pierre’s brother Nelson is a forward on the senior team’s books, but he’s spending the year with the reserves.

And one is the son of an American pioneer in Europe: Jeremiah White III. His father played in Greece, France, Denmark, and other countries in the 2000s, and reached the national team once in 2008.

The Union’s under-15 squad has made an even bigger splash. After beating Inter Miami, Sporting Kansas City, and Spain’s Valencia in the group stage, the team beat European powers Arsenal and Real Madrid in the knockout rounds to reach the semifinals.

Yes, you read that right: A Union youth team beat Arsenal and Real Madrid. Even more remarkable, the Arsenal win was by a whopping 4-1. Cavan Sullivan, Anisse Saidi (twice), and Mateo Gallegos scored the goals.

The Real Madrid win was on penalty kicks after a scoreless tie Thursday. Goalkeeper Alex Smith made two saves in the shootout.

» READ MORE: Union striker prospect Nelson Pierre earns a promotion to MLS at age 17

Sullivan is the group’s top attraction, and not just because he’s Quinn’s younger brother. Cavan has long been touted as the bigger prospect by coaches and scouts, and has a pile of big European teams watching him. The brothers spent a week at German power Borussia Dortmund in September 2020, and Cavan took another trip there last May.

The entire Union organization knows how good he is, and Curtin isn’t afraid to say so out loud.

“Cavan Sullivan has the ability to become, I’ll just say, a household name,” he said this week. “He’s doing really big things.”

Both teams’ semifinals are set for Saturday. The under-15s will play Orlando City at noon, and the under-17s will play Los Angeles FC at 5 p.m.

The games will be streamed on Apple’s MLS Season Pass platform, the same place where the big-league team’s games are. Scroll down a ways on the Season Pass home page and you’ll see a section for the tournament.

» READ MORE: Born to soccer, Northeast Philly's Quinn Sullivan and Brandan Craig aim for the 2026 World Cup