The idea of Gee’s practice principle is that people need to have enough practice in something they enjoy, something they aren’t bored with in order to excel in it. I agree, in sports a player won’t do good, or may not even play if they aren’t enjoying the position they are assigned. I have some friends that play soccer, one of them being a pretty good player. He got assigned a position he didn’t want to play for, and thought of not playing for that team anymore unless he is assigned a better position, one that gets him more play time. This proves the principle, as he was discouraged based on the circumstances he had to practice, or participate under.
I can relate to your friend. When we have to do something that we are not interested in, we have no motivation to do it. In your friend’s case, he could choose not to play in the team anymore because he probably voluntarly joined the team. However, if it was an course in college that he dislike, he would have to continue to take it in order to graduate. Sometimes, we can quit things that we dislike, but other times we are forced to do it.