The teen was a late substitute in the 3-0 win.
Arteta explained afterwards: "Well, the thought was as well from yesterday, the fact that we had to play Christian (Norgaard) as well, we had to really consider it because we were playing a really good side that had some really good results in the Champions League at home as well, but we knew that at some point we had to use him.
"So, he was ready, he was prepared, he can play as a centre-back or as a full-back and I'm delighted. He's so young, 16 still, and he's playing in the Champions League. So yeah, what a great night for him as well."
At 16, Salmon ranks as the sixth-youngest player ever to feature in the competition proper:
15y 308d Max Dowman, Arsenal, 04/11/2025
16y 18d Youssoufa Moukoko, Borussia Dortmund, 08/12/2020
16y 68d Lamine Yamal, Barcelona, 19/09/2023
16y 86d Céléstine Babayaro, Anderlecht, 23/11/1994
16y 102d Rayan Cherki, Lyon, 27/11/2019
16y 103d Marli Salmon, Arsenal, 10/12/2025