FAIRFAX, Va. — Brenden Aaronson looked a few inches taller as he got off the bus with the U.S. national team at Thursday’s practice.

And why shouldn't he?

The 18-year-old Medford native is in the midst of his first senior U.S. training camp, a great honor for a Rookie of the Year-worthy season with the Union.

Now he has stepped up to an even higher level.

“The speed, definitely,” Aaronson said. “Everybody here is super-clean and just super-fast on the ball. They know what they want to do next.”

Aaronson has shown this year that he has the same instinct. Whether or not he plays in the Americans’ two upcoming Concacaf Nations League games, he at least has the chance to make an impression.

"All the guys here that I've looked up to the past couple years... it's kind of surreal being here and seeing them all playing and training," he said. "It teaches you a lot of things, and they want to push you to get better."

He didn't even mind a bit of rookie initiation: carrying the water jugs when camp opened on Monday.

“Hey, it’s OK — you’ve got to do what you’ve got to do on the first day,” he said. “The group is a great group of guys. They all came up to me and shook my hand, looked me right me in the eye.”

Berhalter gave Aaronson an endorsement during his news conference Thursday.

“He’s been good,” Berhalter said. “It’s less about us seeing him, that’s one component to it, but it’s about exposing him to this environment, and him being around these long-term pros and understanding what it’s like to be part of the men’s national team. He’s done a good job, though. It’s been great to see him in camp.”

Aaronson also has the Union’s upcoming playoff game on his mind. But he doesn’t want to hold anything back in his national team audition.

“This is my country, so I’m going to do whatever I can," he said. "I’m sure that I’ll be fine to go back, because I’m 18 years old and it won’t have a toll on my body. So I’m going to let it all out here, and then go back and let it all out with the Union.”

The Americans host Cuba on Friday in Washington (7 p.m., Fox Sports 1, UniMás and TUDN), then face Canada in Toronto on Tuesday (7:30 p.m., ESPN2, UniMás and TUDN). Both games have real stakes, as Nations League results count toward qualifying for the 2021 Gold Cup and 2022 World Cup.

Cuba should be easily beatable, but Canada will be a test. Though the U.S. is a clear favorite, a bit of next-door-neighbor rivalry will liven up the contest.

Down south, though, the American fan base remains skeptical. As of Thursday afternoon, just 11,500 tickets were sold for the Cuba game at 20,000-seat Audi Field.

Coincidentally, Thursday was two years to the day since the loss at Trinidad & Tobago that kept the U.S. out of last year’s World Cup. The lukewarm box office figure shows scars from back then have yet to heal.