Just rotating tht squad is not enough!, you must keep your condition and morale up to near maximum and even then that does not work everytime (but most), I rotate my squad and always have but there are a few times when I play my weaker team or mix weaker players into my stronger team in the league as to save my best players for better opposition in the cup or champions league!( only when Im playing bottom end league teams).Something else to consider is how much training your doing on that day, dont train till after your last match and if it happens to be late in the day and you have a close next day match then dont train that day! or move the match time if possible, everybody has different targets I personaly have the league so that will take priority over everything thus why I always win the league! trying to go for the treble is very difficult unless you are going to spend or farm lots of tokens, the higher the level the harder it becomes, the more frequent injuries, the harder the teams etc so try to be sensible in what you try to achieve and give your team plenty of rest, to put it into perspective my team used to be 22 50T scouts and still could not win the treble every year!, it still has around 6-8 plus the seasons before so is very strong but again I find it very difficult to manage on 3 fronts!.