I would also argue that there are quiet, unassuming players who are completely unnoticed by those in the stands who are held in high regard by teammates. And just because these players don't visibly display their emotions and desire to win for all to see, it doesn't mean their competitiveness is any less than those who wear it on their sleeves.
And some of those "leaders" who are emotional and rah rah vocally, are not always held in high regard by their other teammates. Their visible and vocal displays are sometimes perceived as a means to curry favor with the coaches.
And I've seen examples of both, kids who were natural leaders on the field and those who were posing in an attempt to further their own cause. But, for the observer sitting in the stands, it might be difficult to tell the difference.