i'd second the months, if not years, of practice... Helu is also paying attention up field for the wrong colored jerseys, and you don't 'bullet' a pitch to a guy that close to you. timing, softness of the pitch, distance from the sideline, are all 'feel' things from thousands of these things in practice.
even in the true 'option days', there were tandems that never quite got it right, and we put the ball on the carpet a helluva lot...