there are different settings for the depth chart that you can choose from. but if your players get tired then the coach will put other players in the game. the coach doesn't really take into consideration that you want players to play 48 minutes across the boards. the way that i would do it would tell the coach to strictly select from the depth chart. then only have one player as an option for a certain position. so if player A is the only option for starter, backup, and reserve then the coach can only choose him and he will get a full 48 minutes. that's at least what i would do if my back was to a wall. but if you pay attention enough then your starters will be able to play for both real games and your other players can start in the scrimmages to make up time.