If the game "decided" that you will lose, you will lose.
Sorry for the English. This is google translate.
I never do test them for their performance... If there is one bad player in a game, the others step up for him everytime for me. I have never had a particularly bad player. One season my AML is a bit better, another season my AMR might be through the roof. However I have never had players who were generally bad. Every player has a bad game here and there, it is the decision of the manager to react and maybe sub him in a game.