Unless... wouldn't it be funny if new FIFA releases were auto-generated from a config file? The developer would only need to update the roster and provide paths to new art assets. Boom, new retail game.
Would you expect those assets to be included in source code, though? Roosters are generally fully customizable and EA games vary little year to year, I wouldn't expect players to ever show up in source.
That depends on how data driven player appearance, animations and behaviors are. I would start with the AI code and see if there are any player specific exceptions (that is, hacks) in there to match a certain play style.