Last Wednesday, Giovanni Reyna started for German titan Borussia Dortmund in the UEFA Champions League, club soccer’s ultimate testing ground.

Three days later, the deft attacker was back in the lineup for a Bundesliga match against the world’s best, Bayern Munich.

On Thursday, he is primed to debut for the U.S. national team, which, with a collection of whiz kids from illustrious European clubs, is entering a period of renewed optimism after missing the last World Cup.

On Friday, Reyna will turn 18.

“People ask me about Gio. I say for a high school senior, he is doing just fine,” his father, Claudio, the former University of Virginia star, U.S. World Cup captain and Hall of Famer, said with a laugh. “At that age, I was playing in state championships; he’s running out into Champions League games.”

Gio’s rise has transpired over 16 months, from promising attacker in MLS’s youth system to one of world soccer’s most prized prospects.

And in an introduction delayed multiple times by the coronavirus pandemic, Reyna this week joined the national team in preparation for friendlies against Wales on Thursday in Swansea and Panama on Monday in Wiener Neustadt, Austria.

“I’ve never really had time to fully think about everything that’s happened,” he said in a phone interview from training camp in Cardiff, Wales. “When I think about it, something else happens. I am more of a person who looks to the future. I’m never really satisfied — save the best for the future.”

Indeed, the blinding rate of milestones has blurred Reyna’s appreciation for what he has accomplished.

In summer 2019, he moved from New York City FC’s academy to Borussia Dortmund’s under-19 squad. By January, he had ascended to the first team.

Since then, he has appeared in 22 Bundesliga matches, starting eight and scoring his first goal in September.

Last month, he had three assists in a 35-minute span. His German Cup and Champions League debuts came in February, and following the pandemic shutdown and summer break, he secured regular playing time.

With both Dortmund and the U.S. program, Reyna is following in the footsteps of Christian Pulisic, 22, a Hershey, Pa., native who bolted to stardom as a teenager before transferring to Chelsea in the Premier League last year for $73 million, an American record.

With Pulisic excelling in London, Reyna beat his U.S. mark as the youngest to appear in a Bundesliga match. He also became the second youngest behind Pulisic to score in the esteemed circuit.

Dortmund’s Erling Haaland, a 20-year-old Norwegian forward who has partnered with Reyna on several goals since last winter, called his teammate the “American Dream” because “he has a huge future in front of him.”

From afar, Claudio Reyna marvels at his son’s rapid progress.

“I still can’t believe what he’s doing at his age,” said Claudio, sporting director of Austin FC, a 2021 MLS expansion team. “The other day watching him against Bayern Munich, he’s playing against the best team in the world, doing what he’s doing. There’s nothing but proud feelings, knowing all these experiences are a foundation for his career.”

As Gio’s club career accelerates, his national team tenure is about to begin. He will join a squad bursting with youthful talent already in the U.S. mix, such as Pulisic, Juventus’s Weston McKennie and RB Leipzig’s Tyler Adams.

The average age of the players summoned to Wales is 22.

“It’s going to take time” for the group to bond and thrive, said Reyna, an attacking midfielder. “At the same time, we have a lot of good players playing at top clubs ready to compete now.”

The plan for all the top young players to start together for the first time Thursday was upended when German club Werder Bremen, citing pandemic guidelines, declined to release forward Josh Sargent. Also, Pulisic has been ruled out with a hamstring injury that sidelined him for several Chelsea matches.

This get-together, the first for European-based players in a year, is the first step in building cohesion leading to the delayed start of 2022 World Cup qualifying in September.

Despite missing the 2018 tournament in Russia, its first absence from the World Cup since 1986, the United States is among the favorites from the Concacaf region to earn one of the three automatic berths.

Reyna is so young, his most vivid World Cup memories go back only to 2014.

“That one was in Brazil, right?” he said, adding he also recalls watching some of the 2010 tournament, held in South Africa.

At age 3, he attended the 2006 World Cup in Germany, where his father captained the U.S. team for the second time. Claudio Reyna was part of four World Cup squads, starting in 1994 at age 20.

Among his 2002 World Cup teammates was Gregg Berhalter, the current U.S. coach. They also played together at St. Benedict’s Prep in Newark.

Berhalter said father and son have “a very similar grace to them, how they move around the field in a very fluid way. … I know Claudio was really competitive; you can see Gio has that competitive fire.”

Gio has sprouted to 6-foot-1, four inches taller than his father and larger than a typical midfielder. He thrives, though, because he has superb technical ability, vision and feel for the game.

Claudio said: “Gio thinks out there. We have the same understanding of the game, the spacing and where your teammates are.”

The elder Reyna also began his pro career in Germany, signing with Bayer Leverkusen after leading Virginia to three consecutive NCAA titles (1991-93). He later played for Glasgow Rangers, Sunderland and Manchester City. Gio was born in England while Claudio was employed by Sunderland.

Claudio is now the lesser-known Reyna.

“The younger generation has no clue who I am,” he said, laughing.

Gio drew soccer influences from both parents. His mother, Danielle, starred at the University of North Carolina alongside Mia Hamm and made six national team appearances in 1993. His parents met in 1994 when the national teams were staying at the same hotel in Southern California.

Gio said his parents never pressured him into pursuing soccer at a high level.

“My dad would always tell me, ‘Play free, have fun, do your thing,’ ” Gio said.

Even now, he said, his father texts similar messages before every match.

“It was never forced,” Claudio said of Gio’s soccer upbringing. “The progress was gradual. Every decision has been made in a calm manner, knowing it’s a journey.”

As part of a low-stress childhood, Gio also played AAU basketball until he was 14 and enjoyed several other sports.

“He wasn’t a kid who sat around and only watched soccer games,” Claudio said. “He was an American kid who loved watching basketball and American football and college sports. I would take him to different sporting events. I always instilled in him to just be him.”

His soccer abilities were undeniable, and other sports were cast aside. While honing his skills with the youth academy at NYCFC, where his father worked before taking the Austin job, Gio made the U.S. under-15 and under-17 national teams.

Players are typically not permitted to sign abroad until they turn 18, but because family roots afforded him a Portuguese passport as European eligibility, he was able to join Dortmund early. (Pulisic had used a Croatian passport to jump-start his Dortmund career at 16.)

Reyna’s development has not only lifted his standing with Dortmund but launched him into Berhalter’s immediate plans alongside other young U.S. talent.

“Everyone knows this is the start of a new generation,” Gio said. “Everyone is really excited. It’s been one of the things I’ve been waiting for.”