All things in this game, including SA's working, are the result of a battle of the offensive and defensive players rolls, and head fake is no different. It probably won't make much different in how often it fires, but the higher your agility, the higher your head fake roll, the greater the chance of the defender being faked. The description for juke implies that agilty is the main trigger for headfake effectiveness as well.
Its not simply you have 10 headfake, pass/fail, but rather your head fake, agility, and a few other things I'm guessing (conf/vision?) make up your roll, which is then compared to the defenders roll (based on maybe vision/agility/conf) and the head fake either works or doesn't based on which roll is higher. There is also a random factor to each roll as well
All imo of course.
