I think if a player wants more money because he "outplayed his contract", then pay him more if he hasn't been getting into trouble. But, put in a clause stating if he "under plays his contract" team able to reduce his pay accordingly. Injuries aside.
I went to my proctologist and as I was bending over I heard him say "calm down Smith, calm down Smith" I looked back and told him "Doctor, my last name is Green, not Smith" and he said "I know, Smith is me"