Brenden Aaronson has a lot on his mind right now, and it’s easy to see why.

In addition to being at U.S. national team camp ahead of Wednesday’s year-ending game vs. El Salvador (7:30 p.m., ESPNews, UniMas, TUDN), he’s getting ready to make his big move to Red Bull Salzburg in early January.

And just a few hours before Aaronson is likely to play for his country, his new club plays its biggest game of the season: a win-and-advance Champions League group stage finale at home against Spanish power Atletico Madrid (3 p.m., Galavision). If Salzburg prevails, Aaronson might get to play in world soccer’s biggest club tournament not long after arriving in Austria. The knockout stages start Feb. 1 with the round of 16.

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Aaronson is allowing himself to be excited, and to dream of playing in the Champions League soon.

“I’m definitely going to watch the [Salzburg] game,” he said on a Zoom call with nationwide media Monday afternoon, a sign on its own of how big a deal the 20-year-old Medford native has become in American soccer.

“But right after that,” he added, “all my focus goes right to the national team.”

That’s where his focus has been for the last few days, as part of a U.S. squad with many promising young players — including his former Union teammate Mark McKenzie.

“I think it’s just staying focused on each team that I come to,” Aaronson said. “I was all focused with the Union at one point, now I’m all focused with the national team because we have a big game against El Salvador, and I think it’ll be good for me to be a part of the team and hopefully get in … Next coming up is Salzburg, and just trying to make my mark there.”

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Though he has tried to take it one team at a time, there’s been one area where he’s had to do all his homework at once: studying tactical playbooks. Gregg Berhalter’s 4-3-3 is different from the Union’s 4-4-2 diamond and backup 4-2-3-1, which is in turn different from Salzburg’s 4-2-2-2.

If that all sounds like a weird math equation, that’s fair. Here’s the simple way to put it: With the Union, Aaronson usually played at the top of a diamond-shaped four-man midfield, or on the left in a four- or five-man midfield. U.S. coach Gregg Berhalter plays a midfield triangle with two men in front of one, and Aaronson projects to be one of those front two.

“I really enjoy playing that position, because I can get forward and I can defend,” Aaronson said. “I want to have a stake in this team and be a part of it for the future. And I think that this camp, and getting this game against El Salvador, is big for me because I want to show what I can do after the year I’ve had.”

Salzburg, coached by Princeton alum Jesse Marsch, puts two attacking midfielders in front of two defensive midfielders, and gives the two attackers lots of freedom. Aaronson projects as one of those two, lining up toward the left side.

If you watch Salzburg-Atletico, you’ll see that one of Salzburg’s current attacking midfielders, 20-year-old Hungarian Domonik Szoboszlai, is one of the most sought-after prospects in Europe. And if Salzburg sells him during the winter transfer window, which is quite possible, Aaronson could be his replacement.

“The way they play, it’s high-tempo, always looking to play forward, dynamic, all that kind of stuff — I think it fits my game,” Aaronson said. “I feel like I have the mentality to go there and do what they do, which is run, press, play forward, and hopefully it will go from there.”

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