Currently in the game it is easy to entice good players to come to the club by offering massive performance bonuses (relative to the league). Players see the bonus and think it's a sure thing, sign on, and then never get it because they get benched towards the end of the season. Effectively, the manager is taking advantage of the player by offering more money than the player ultimately will receive or the club will pay. This hurts the real life sport as well as the spirit of the game.
Example: Player has reached 29 goals this season out of a goal goal of 30. With six games remaining in the season, the manager chooses not to play the player for the rest of the season, not even on the bench, thus shorting the player on their amazing and deserving performance.
Suggestion: Make players unhappy if they are close to reaching their performance bonus but have been benched or not even picked for several games (increasing unhappiness penalty from benched to not being in the lineup at all).