I don't think there are any hidden attributes. The game is not that well programmed.
It's totally useless keeping tabs on players performances. Ive had players score 2 goals and getting a rating of 6. In my last match I won 1-0, my CB scored the winning goal was part of a defence that kept a clean sheet and he got a 5! Then the other way ive had players who haven't had one mention in the game and got an 8, ive even had ST's who had several scoring chances and missed the lot but still managed to get an 8.
Im afraid players match ratings are no way near a sign of how a player has played. In my opinion they are just random numbers.