Playing time ups conditioning which moderates fatigue recovery rates. Having higher conditioning will allow for better chances not to get injuried when starters are playing 70 to 100 snaps for the first game.
Upping play familiarity on both sides will produce slightly better results . Scouting does that too but is really beneficial in big games cause you get an in game boost to that play if it is overused by your opponent .
I use preseason for those two things . Playing with the depth depth chart and fatigue settings under misc. Along with overides , under depth chart , the misc. Section has a bunch of setting to change to get who you want on the feild learning .
Thats the balance ....... learning , but conditioning . You can sit a vet in the nfl for the preseason . Do that here and you star player is most likely going to injuried that first game.
Unless they are qb... They don't get injuries as much...same for K and punter . They don't get injuried at all.
I like to get my young guys a bit more snaps in preseason but watch for low accuracy qbs they will make any good offense look bad. Those guys need 50 + to get any real good film to study for game to game changes. So unless your building his knowledge of stuff its better to let them mature on the bench.