My favorite ever was FM14, when I was managing Dortmund. Picked up a french newgen from Panathinaikos for mere 2m. Which I included in the French national team for the euros as a backup left winger, before making the signing. (I was the manager of France at that time as well) He was on fire as a...
I tend to put the unhappy players on as a late substitute in a won game. After a while he gets the morale up, because of the won games and post-match comments.
I'm not talking about the match rating... I'm talking about how and why it only counts towards their development if they play 15+ min. What you are saying it seems that subbing on someone after 75th minute is useless as it doesn't help their development.