Originally Posted by Ash_Smith
Sennoc - timing of the foot placement on the volly depends on the height of contact. Low volley and the foot does plant just before the contact (step before the hit). Mid-high volley and the contact takes place during the step (step during the hit) and for high volleys the contact comes first (contact before the step).
I analyzed almost every replay of Federer's volleys during last 5 years. Thousands of shots. I saw just a few examples when his foot landed on the ground at contact. He lost all these volleys. He hits in the air. Check other good volleyers. Henman. Sampras. Check them frame by frame.