Sully you totally missed the point. Motivation is a factor that deals with individual players.
Out of position has little to do with player form in one match, but have negative impact on his motivation for later games.

When you have players with fluctuating form it is caused by non-optimal player management.

Your answer is simple, how can you make your players form clean if you don't believe player performance could be manipulated? You will rely on luck because you don't know or never find out how to do it.