Keep your eye on the ball for the entire time. Never let it out of your sight when possible. Watching other players such as Federer and Nadal ( Of course you aren't them, but they are a good example for this ), you would see them watching the ball fly off their racquets...
Close, but not entirely true. Yes, it is true that elite players do
not look at the spot or area to where they want the ball to go. Instead, they
visualize where they want the ball to go. Visualization is a very powerful tool that should be developed ball all intermediate players. Even novices can use it to some extent. After a little bit of practice, a novice player can watch a ball trajectory and predict or visualize to some extent where the ball will bounce.
As they get better at this they will also learn to predict/visualize how the ball will bounce and visualize/determine where they should move to intercept the incoming ball. After further experience, players learn to visualize where they want the ball to go. At times, we will just reflex the ball back but, most of the time, decent players will intentionally put the ball where they want it either by visualizing the shot or visualizing the intended location. The better we get at visualization, the better our subconscious mind figures out how to make the visualized image happen.
Ok, let's get back to the subject of watching the ball. While elite players do watch the ball quite a bit of the time, they do not watch the ball all the time. One time when elite players are not watching the ball is during the forward swing on groundstrokes (and volleys). For most incoming balls, it is actually impossible for our eyes to track it all the way into the stringbed. When most balls get very close, the ball traverses our field of vision so quickly, the motion exceeds out visual pursuit velocity (measured in degrees/sec).
Some years back, I posted a link that showed a slow motion (high-speed) video of Federer swinging at an incoming ball. The video showed that Roger's eyes appeared to get to the
contact point before the ball did (as he commenced his forward swing). With this eye movement to the contact point, he has obviously stopped watching the ball. Roger continues to fixate on the contact point as the ball makes contact (for 4-5 ms). His eyes stay on the contact point for most of the rest of his forward swing even tho' the ball is speeding away. Clearly, he is not watching the ball during this time either. During the time Roger's eyes are fixated in the contact point, he keeps his head very still. Also, during this time, he is employing visualization in order to direct his shot.
Apparently, studies by
Yandell,
Vickers (The Quiet Eye),
Lafont and others have come to the same conclusions that I have. Here are a couple of links that discuss this:
http://www.ingentaconnect.com/content/uwic/ujpa/2008/00000008/00000001/art00010
http://www.damienlafont.com/tennis/six-good-reasons-to-keep-your-eyes-off-the-ball