My opinion concerning defensive players:
AWR-How well the defender performs his assignment for the play and how well he adjusts to the play as it happens. A higher AWR LB, for example, is more likely to super jump and snag a ball in the air than a lower AWR LB. I think AWR combines with other ratings to enhance them.
EX: A DB with high AWR and high MCV should play great man to man defense and, for example, defend the 10 yard hitch very well. A DB with low AWR/high MCV or low MCV and high AWR would not cover this route as well and the WR would get more seperation.
I believe higher AWR also enhances how well the defender recognizes a "spot light" WR in his zone and how well he plays the ball in the air.
PRC-How well the defender reads run/pass.
Just my opinion as EA either can't or won't explain these to us in detail.