I'm not sure what you're getting at. I dropped my left back for a lesser quality left back because the inferior player is in better form. I dropped one of my MCs because he's average and my team suffers with creativity even though he's a playmaker.

If you're saying a player performs bad because he's coded to then I'd agree to some degree. Maybe they just don't work in that particular formation. You just need to get a feel of how your team performs.