Asunto: Question about training/team size

As a new team, I am coming to the understanding that, for the most part, advanced training players gives them 96% training in one league game. I also notice we have two league games a week now, plus a third friendly possible (which I definitely need from a money standpoint). So, I'm trying to figure out just how many players I should keep on my roster. At this point, I'm thinking about 22, 11 for the starters/training/league games, and 11 backups at low wages to use in friendlies. Unless friendlies don't cause injuries? I've read they don't matter in arcade games, but not sure about friendlies.

I have a basic understanding/memory of how training works, but there are some minor nuances I haven't figured out yet.

Thanks