For me it is different. Whenever my player does negative stuff he gets a 6 or a 5.
I did sub one player that wasn't mentioned at all during 60 minutes and the commentary says "great match from him, he leaves the field" and he ends up with a 7 or even 8.
But I personally don't look at the ratings much. I just make sure my team is in good condition and superb morale in every match...