The rating of a player is calculated from the effective values of his key attributes. The effective value of an attribute is based on the actual value of that attribute and the player's Experience.
If the Experience of the player is higher than the attribute, then the effective value of that attribute is same as it's actual value.
If the attribute is higher than Experience, then effective value of that attribute is the average of its actual value and Experience.
Each attribute provides a certain weightage towards the rating calculation as detailed in the below table. These weightages are applied on the calculated effective value for each of these attributes to arrive at the rating of the player.
The rating is an estimated performance potential of a player. However, there are a lot of other factors that could affect a player's performance during a match. And the match engine always uses the individual attributes for simulation of match events and does not consider the rating at all. The actual performance of the player in a match will depend on how well his attributes are suited to those situations during the simulation. So always look at the individual attributes while evaluating a player rather than blindly going by his rating.