On your groundstrokes, should you take the racket back as soon as the ball is coming to you? Absolutely not! Stop thinking about jamming the racket back when the ball is coming to you. This is too mechanical and robot-like. You must learn to be more instinctive and automatic. How? Take the racket back when you are about to hit the ball, not while you are running to hit the ball. Taking the racket back too soon is unnatural and is not compatible with the principles of timing and rhythm.
Do you think I have gone wacky? Not so! At least not in the way you think. Here is another question for you. Have you ever seen a pro take his racket back, then proceed to run with the racket hanging behind him? Watch the pros the next time and see what you think.
You will be surprised to discover the racket goes back as they are about to hit. They may have a slight turn in the direction they are running, but the full swing begins when they are about to hit. If I were you, I would forget about even thinking about taking the racket back. Let it happen naturally as you approach the ball. It is time to begin playing more like a pro. Do not fall for the rigid, conventional method of taking the racket back like a robot. I'm not sure where this came from, but it's a myth. It does not hold up under true playing application.
One of the reasons the pros take the racket back later than you would have expected is because it is more natural to run to meet the ball with the racket in front of you rather than behind. The pros may take a slight turn in the direction of the ball, but the racket does not go all the way back until they are ready to hit the ball. I usually demonstrate to my students how silly it looks to run to meet the ball with the racket behind. Then I ask if they have ever seen a pro look like that. They usually laugh. You can click here to watch a short video from one of my tennis clinics years ago:
Tennis Video from Tom Veneziano - Don't Take the Racket Back!
Another reason the pros wait to take the racket back is because the backswing is part of the timing and rhythm of hitting the ball. If the racket is back too soon they will lose the rhythm and feel of the shot and become too mechanical.
The lesson here is to not take the racket back too soon. Wait until you are near the ball and about to swing. As I said earlier, if I were you I would not even think about taking the racket back. Just let it happen naturally. The more you practice letting the racket go back naturally, the better your timing and rhythm will become. Do not fall prey to the myth of taking the racket back too soon.