Gio Reyna in Dortmund's Champions League squad

Reyna, 16, is one of 23 outfield players included in Lucien Favre's 31-man ensemble, despite not yet playing a single minute of competitive football for the senior side.

The American, who was signed from the New York City FC academy in the summer, played in pre-season friendlies against Seattle Sounders and Liverpool. He currently plies his trade with the BVB U19s in the Bundesliga West, where he has registered one goal and four assists in his first four matches of the 2019/20 campaign.

He is the son of former USA international, Claudio Reyna.

Reyna is among Dortmund's A-list, which UEFA regulations stipulate should be made up of up to 25 representatives, including two goalkeepers and at least eight 'locally trained players'.

According to UEFA, there are two ways for players to qualify as 'locally trained'.

1) Club-trained players – players who were on a club’s books for three years between the ages of 15 and 21

2) Association-trained players – players who were on another club's books in the same association for three years between the ages of 15 and 21. No club can have more than four association-trained players among their eight 'local' nominees on List A. If the club doesn’t meet the criteria of eight 'homegrown' players, the 25-player list will be trimmed.

Watch: Gio Reyna in action on Dortmund's summer US tour

Dortmund have also submitted a B-list, comprising six players born on or after 1 January 1998, and who have been eligible to play for the club for an uninterrupted period of two years since their 15th birthday.

There is no limit on the number of B-list players, but the list must be submitted by midnight on the day before a match.

The Bundesliga's leading assist provider in 2018/19, Jadon Sancho, is one of six names on Favre's initial B-list. The other five are Dortmund youth players.

Dortmund have been drawn in Champions League Group F alongside Barcelona, Inter Milan and Slavia Prague.

The Black-Yellows begin their Champions League campaign at home to defending La Liga champions Barca on 17 September.

Dortmund's UEFA Champions League squad in full

Goalkeepers: Roman Bürki, Marwin Hitz, Eric Oelschlägel, Luca Unbehaun*

Defenders: Manuel Akanji, Leonardo Balerdi, Achraf Hakimi, Raphael Guerreiro, Mats Hummels, Mateu Morey, Lukasz Piszczek, Marcel Schmelzer, Nico Schulz, Dan-Axel Zagadou

Midfielders: Jano Baxmann*, Julian Brandt, Mahmoud Dahoud, Thomas Delaney, Patrick Osterhage*, Manuel Pherai*, Tobias Raschl*, Marco Reus, Gio Reyna, Dommink Wanner*, Julian Weigl, Axel Witsel

Forwards: Paco Alcacer, Jacob Bruun Larsen, Mario Götze, Thorgan Hazard, Jadon Sancho*

*B-list players