I feel like if the problem is with teammates calling about attitude helps as long as the coach relationship is good. Obviously a player with a better personality is more likely to react well to a phone call about discipline. Another thing I have noticed is that if you have a really big freshman class it is often more difficult to maintain player relationships.
I think the playing time issue can be very frustrating. I wish the game would not punish you for a player not getting minutes because of foul trouble. Sometimes, I have seen a starter mysteriously benched for no apparent reason when simulating.