The 19-year-old broke into the Dortmund first team in early 2020 and soon established himself as an integral member of the side thanks to his fearless approach, direct running and eye for a pass in the final third.
Now a fully fledged Bundesliga professional with six goals in 52 top-flight outings, the nine-time USMNT midfielder is happy to pass on tips from his experience to help a fresh wave of star-spangled youngsters hoping to make the grade in Germany.
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In the January transfer window alone, Ricardo Pepi (Augsburg), George Bello (Arminia Bielefeld), Justin Che (Hoffenheim) and Kevin Paredes (Wolfsburg) all swapped the MLS for the Bundesliga, joining compatriots Joe Scally, Chris Richards and Tyler Adams, among others, at Germany's top table.
Asked during a media roundtable ahead of Dortmund's Matchday 24 trip to Augsburg on Sunday whether he offered assistance to the newcomers, Reyna revealed that he does so with pleasure.
"I was talking to Pepi yesterday or the day before," he said. "We were just trying to chat. He was reaching out for some help. Obviously it's a big difference from living in America and playing in the Bundesliga, so I'm there for them if they need anything.
"I've told all of them that. I know how tough it can be here, especially with a long, hard season. They've just got to keep on grinding and I'm sure they'll all do very well here. I'm there for them if they need help."
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Reyna has had to lean on others for support recently too, having spent much of the current season on the sidelines with injury. After scoring two goals in Dortmund's first three Bundesliga games of the season, he sustained a muscle injury on international duty in August that kept him out of action until early February.
The BVB No.7 then suffered a further setback when he was taken off the pitch against Borussia Mönchengladbach last Sunday with a thigh complaint - an injury that proved not to be as serious as first feared.
"I'm doing well, I'm doing really well," he said. "I'm seeing a few people that should and will be able to help me and get me back to 100 percent very soon. It was pretty scary.
"The five months [on the sidelines with the previous injury] were really complicated and it was really hard because I'm happiest when I'm playing. The thought that maybe I was going to be out for another extended period of time with the same injury was tough to take in, but I'm just happy it's nothing serious and I should be back soon."
Watch: Reyna's fresh injury blow
That will be music to the ears of head coach Marco Rose, who will need Reyna as BVB bid to keep up the pressure on league leaders Bayern Munich in the last third of the season.
With Marco Reus, Donyell Malen, Julian Brandt and Thorgan Hazard all competing for places in attacking midfield behind Erling Haaland, Reyna faces a fight to regain his regular starting slot, but believes his positional flexibility will stand him in good stead.
"I don't really want to put a position out there," he said, when asked where he prefers to play. "I think that's one of the strengths of my game that I'm versatile. I can play on the left, in the middle, or on the right. I grew up playing in the middle as an attacking midfielder but I think with the way we play here, it's very free-flowing and very open for all the attackers to be creative.
"If I start on the right it doesn't mean that I'm going to stay there," he continued. "We have other guys like Marco, Donny, Julian and Thorgan that can also play in any of those kind of positions. I might start on the right and end up in the middle at some point, or start in the middle and end up on the left, so we try to switch it up, stay creative and keep the opposing defenders on their toes."
And, if all goes to plan, that will include defenders on the international stage in Qatar later this year: "I'm really looking forward to hopefully going to the next [USMNT] camp [in March] and being able to go to the World Cup."