Well, sometimes you can see that for example morale drops because a player not provided assists or not scored for a while. But again it's common for mc to not provide assists just because they do not make those assists anyway. But for most players you just can guess why it's dropped because there are no explanation.
C'mon top eleven is a guess game - where you always must guess what certain function or action does in the game .
There is not proof that morale even do something in a game. You can guess from your experience but other could say on the contrary.