Balancing the squad depth

[Diegas]

Wasnt sure if to post here, or scouting forum, but still decided that this thing takes some some tactical planning and brain using, so posted it here.

So here's the problem:

Last season I thought I will be balancing my team: 3 keyplayers, 5 first teamers, some rotation players and some backup. Got rid of all the rest. So those 8-7 would always play, and up to 4 rotation players. That worked out pretty well till I got hit by injuries - 5 of my always starting 8 Eventually that resulted in 7loses and 1 draw streak which caused me european qualification

So this season I got adequate covers for my key players. E.g., I have two star DMCs, though I can use only one at a time(same issue with DCs, AMLs and STs). Now I've got them all unhappy caude they think they are not in the first team! I tried to balance their played games, but that doesnt help. And I'm sure their unhapiness results in worse results on the pitch.

So the question is - how to balance the squad depth that you could have:

* Decent backup for injuries;

* Backup for possible formation change (e.g. I will decide to play 2 STs tactic instead of 1 ST tactic);

* AND Avoid them complaining about not being first team.