alot of it comes back to what i mentioned earlier : GAME SHAPE!
do not under estimate it, it can be your best friend, or a thorn in your side....
theoretically, you want your players to play between 60-80 mins per game. on average, a starter plays 30 mins per game, 3 games per week (2 league and 1 either cup or scrimmage) so player would play 90 mins per week if he started all 3 games..
in that scenario, the game shape would either stay at current level, or drop, and the effect of a low game shape is huge.
so, a big part of your week comes down to strategising, so you dont kill game shape.. so if bainsy thought your game tonight was a guareenteed win, and the cup game was a challenge, he may have used tonights game for trainees, to get them their training minutes, and rested some guns so he could bring them out for the cup game, and not jeopardise game shape.
it is all a big juggling act.. The way around it of course, is to forget trainees, buy older players and train game shape each week.. i find few can pull off this method, as you need serious $$ and infrastructure behind you to get the right players, and of course your team doesnt get better, so if you promote, staying up could be a challenge, as could be selling old farts :D we had a guy in this league a few seasons ago who tried that and epic failed and relegated :(