Are you using custom plays or the basic AI inputs?
The players individual tactic moves the player relative to the setting in the AI. If you go -100 on the player tactic and 1 yard on the AI setting, he'll give a 0 yard cushion. +100 and 1 yard would give a 2 yard cushion. 0(center) and 1 yard gives 1 yard...etc.
Really short cusions make a player more vulnerable to getting faked, losing the WR on a cut, or getting strait toasted by speed. But they are in much better position to defend the underneath routes.
Deeper cushions make a player more vulnerable to underneath routes like crosses and stops, but are less likely to fall for a fake or get beat deep.
Seems like high vision is better for big cushions and high agility is better for short cushions, but the better CB will usually be able to play closer.
I'm rambling now, I don't know if I even answered your question.
