judging player ability/potential

I dug around and couldn't find the answer, but my question is this: how does my ability to judge ability dictate what I see in the game?

like for a certain player that's been scouted, is what I see the scouts opinion? and then once he's on my team, is what I see my opinion? how awry can the attributes be if I have a poor ability?

If you scout a player by a scouter you will see the opinion of scouter. When will be in your team; you will see the opinion of your Assistant Manager (or the one which have set in responsibilities).