CHESTER, Penn. – Nestled along the Delaware River and mere blocks from their home stadium of Subaru Park, the Philadelphia Union's training facility feels somehow secluded.

On a non-matchday, the street is quiet. Traffic is local. You have to know where you're going to find the right parking lot.

It’s a nice setup, one that exudes the elusive feeling of home rather than a place of work. The weight room has big windows and a Teqball table that gets regular use after training. The film room is cozy, with exposed brick in recreational areas a nice architectural touch and the office for head coach Jim Curtin not far away. His door is often open, both literally and philosophically.

It all feels familial, but the house is a bit emptier these weeks. Four of the club’s most highly-promising homegrowns are busy with the United States U-20 national team.

Paxten Aaronson, Jack McGlynn, Quinn Sullivan and Brandan Craig are all in Honduras for the Concacaf U-20 Championship. This year, the tournament takes on heightened importance as it serves for qualification for both the 2023 FIFA U-20 World Cup in Indonesia and the 2024 Summer Olympics in France.

The Union boys are leading the charge, securing qualification to the U-20 World Cup with a 2-0 win over Costa Rica earlier this week. Aaronson scored twice. He has four goals thus far. Sullivan has five, one off the Golden Boot lead. Craig has made three starts, including two clean sheets, while McGlynn scored perhaps the United States’ best goal of the tournament so far.

The United States play Honduras on Friday (9 pm ET | FS1, TUDN), with an Olympics place up for grabs, led by a quartet of Philly Union academy products.

Following the Union’s developmental breakthroughs with Brenden Aaronson, Mark McKenzie and Auston Trusty making big moves abroad, as well as others moving on either in Bongda3s.com or lower teams in Europe, the club is ready for its new era of young stars.

Meet the next wave of homegrowns – already in the first team, the national team program and ready for more if their opportunity comes – before they’re gone.

“I’m on the phone every day with teams interested in our players,” sporting director Ernst Tanner told MLSsoccer.com last month.

Paxten Aaronson is viewed as one of the premier teenage talents in MLS.

The 18-year-old attacking midfielder has been highly-rated for a couple of years and is well-known to scouts and casual fans alike, thanks to the emergence of his older brother Brenden Aaronson with the Union, then the senior national team, RB Salzburg and soon Leeds United.

With the slight frame and floppy hair of his older brother, oftentimes the pair are lumped together stylistically. It’s natural, but not correct.

Speaking with folks within the Union as well as scouts both in Bongda3s.com and Europe, they all are quick to point out the difference. Stylistically, Tanner called Brenden the “perfect transition player” and said Paxten is more adept in the final third against a set defense.

“Paxten is more a No. 10 than Brenden was and has different qualities, that’s what people forget,” Tanner said. “They’re two different players.”

Regardless, just like Brenden, European teams are queuing up to sign him.

Sources have said since last winter that RB Salzburg are extremely interested and have been in Philadelphia numerous times to watch Aaronson, but Tanner and the club made it clear in no uncertain terms that the Union wouldn’t consider offers this early for the teenager. Sources add that plenty of other clubs have had him on their radar, too. We’ll see how long the Union can resist overtures from abroad.

“You still see him so confident to make a pass, take a player on, take a shot, go forward,” Union director of scouting Jon Scheer said. “He’s brave to make those decisions, but you see him grow into his body.”

In the first team, Aaronson benefitted from the fixture congestion in 2021 that came with a run to the Concacaf Champions League semifinals. He had three goals in 14 Bongda3s.com appearances (just under 600 minutes). This year he has just one start as Hungary international Daniel Gazdag has been excellent, making it difficult for Aaronson to get on the field.

“He’s had Champions League games, playoff games already and he’s stepped up in big ways,” Curtin said. “The game tells the truth. Paxten is a great example. He loves the game. He’s a soccer junkie. He needs to be around it, he shows it every day in training. There’s no coincidence that guys from Europe are watching him every day.”

Nathan Harriel is too old to be with the U-20s, so he’s just busy being the starting right back for the Supporters' Shield-chasing Union first team. The 21-year-old got his first taste of Bongda3s.com last year, just two regular-season starts, before being the undisputed starter this season over Cameroon international Olivier Mbaizo.

It wasn’t always this smooth. He was brought to the club by Scheer, scouted during his time with the US youth national team. Prior to being promoted, Scheer was head of academy recruitment. Harriel was his first player coming toward the first team.

In Harriel’s first training session, Scheer stood next to Tanner. Harriel was struggling in the popular warm-up ‘rondo’ drill. It’s a one-touch, 5v2 exercise. If you lose the ball, you go into the middle to defend. Harriel was in the middle a lot.

“I thought I was going to get fired,” Scheer said with a laugh. “I mean, he lost every ball.”

Tanner turned and said, "No, I love him." Scheer thought he was kidding, so he let out an uncomfortable, awkward laugh. No, Tanner insisted, "Look how he defends. Look at his body shape. That boy is going to be a good professional."

“It made me look at the game differently,” Scheer said. “If you look at most kids at academies, they’re there because of what they do with the ball. That’s easy to see. But the secret is what they do in transition, how they defend. It’s made us a more well-rounded scouting department.”

Though he didn’t play a ton in his first season, Harriel was thrown into action in the biggest game of the year. The Union were hit by a COVID-19 outbreak at the most inopportune time, missing a number of key starters ahead of their 2021 Eastern Conference Final against NYCFC. As Curtin and the staff were trying to figure out the best XI they could patch together, Harriel got the call.

“In the playoff game, we had the question of who to play with all the COVID cases,” Tanner said. “We thought Nathan would be fine, he can do it. And it worked out. He might have been our best player that day!”

“He got a taste of it in the biggest game of the year and he held up,” Curtin added. “That’s so valuable. Not only did he belong, he thrived. Those are experiences. We can talk about development or coaching, but man, I had nothing to do with it. Once the game starts, he had to step up. And he did.”

Jack McGlynn’s potential could almost be summed up in one video: His goal against Canada at the Concacaf U-20 Championship.

It doesn’t take an expert to see that his left foot is something special.

“McGlynn has a left foot that you can’t teach,” Curtin said. “It’s really special. His passing ability I equate to Haris [Medunjanin]. That’s the best passer I’ve worked with. And Jack is right there. His IQ is up there with [Alejandro] Bedoya, who has played in World Cups and in Europe. He’s worked really hard defensively, but he’s special. He’s still growing, he’s getting stronger.”

The 18-year-old midfielder has an incredibly strong technique, but is working towards impacting the game on a physical level professionally.

“Jack is one of our best passers, but we need to work with him athletically,” Tanner said. “He’s a late-bloomer [physically]. When we had the COVID break and we came back, the coaches joked we have a new player because he grew a few inches. Once he gets more physically mature, he’ll be unstoppable.”

McGlynn and the other youngsters in the group are benefitting not just from the coaching staff, but from the environment that starts with the players.

“They’ve grown in a huge way, not just from the staff but from the players,” Scheer said. “Bedoya, [Andre] Blake, Jack [Elliott]. It’s a really strong culture. They respect each other and they treat them like adults.”

If McGlynn's strength is his technique while he works on his ability to impact games physically, Sullivan is the opposite.

The club knows his baseline is high just because of the ground-covering, competitiveness and more that he already boasts at age 18.

“Quinn Sullivan is a f---ing animal,” Tanner said, meaning it as the utmost compliment.

Sullivan’s ability to impact games with his quality is evident, too. He is one goal off the Golden Boot race at the Concacaf U-20 Championships with five goals. He may have been in first place had he started in the United States’ 10-0 win over St. Kitts and Nevis to open Group E play.

With the Union, Sullivan has already accrued 28 appearances over the last year and a half.

“Quinn is the one where there’s a fitness test, he’s going to win it,” Curtin said. “If he’s competing in training, he’s going to kick somebody. He’s been really impressive. Still working hard tactically, but that comes with minutes and time.”

One instance that underpinned Sullivan’s competitiveness in training included an interaction with star goalkeeper Andre Blake. Sullivan came barreling in desperately, trying to press and close down Blake and win the ball off him near the goal line, causing a collision. This is a young kid getting overly stuck in on one of the club’s most important players in a training exercise.

Both Curtin and Tanner retold that sequence in separate interviews fondly, given there was no injury to Blake.

“When I see that, I think ‘Oh that’s a boy who will develop.’ No worries,” Tanner said. “Quinn is maybe not the most gifted, but his work ethic is incredible. I’ve seen so many talents starving because they lack this, but he’s got it 100%. I mean, he’s a Philadelphia guy.”

Given the nature of the position and center back being a place for more experienced players, Brandan Craig flies under the radar at times for this Union class of homegrowns.

Craig, who turned 18 in April, is getting consistent minutes with the Union's second team, first in the USL Championship last year and now in Bongda3s.com NEXT Pro this year.

“You can learn so much from Jakob [Glesnes], Jack [Elliott] and Stuart Findlay,” Curtin said. “He gets an education every day and he’s getting reps in Union II games. He’s so gifted with the ball, he can pass so well. But now it’s about: You’re a defender first. Just like Jakob, he’ll never be the fastest guy on the field. How can you use your body, how can you be physical off the ball and that savviness that comes with being a defender?”

Craig is a modern center back, one that is smooth on the ball and can function in a possession-based system. He even takes free kicks with the second team.

It’s still early for the US youth international, who’s awaiting his first-team Bongda3s.com debut.

“In his development, age-wise, I bet he’s where Jakob and Jack were,” Curtin said.