You will have at least nine players who will want to play every game.
Once you know who they are, use them approximately 90% of the time when
they complain about not being used after your first game. Use the other
players in cups and loan some of them, but check your team after every
game. When selling players, just sell them and do not release them,
otherwise it messes up the team. If players need a break for another
game , they will complain. Each year you keep your team happy, the
next year they will not have those problems any longer and be happier
overall with the club.