Could have been Marcus. Could have been someone else from the team. Since Danny got expelled, they'd have to do emergency tryouts. Maybe Zach or Mitchell got on the team.
Could also be an assisting coach? Coach assistant? I forget the proper term. The person who basically helps out the coach in organizing everything. I wouldn't be surprised if a school like Bishop's Gate had one.
Another thought is that it could be a coach from another school entirely who had a student with similar needs who just decided to pipe in and say their two cents. It's Reddit, after all. I'm curious as to what subreddit it would be under, though.