Without knowing for sure, or looking in detail at the moment, I would imagine it is one of the many tactic icon files. Quite often players on a pitch will be controlled by a tactics icon file which will be responsible for how the player appears (face, kit, dot, etc...) as well as how the name appears. The specific one you need might be referenced in the team of the week.xml but, if not, it might end up being a case of trial and error, I'm afraid.