Your serve technique doing more harm than good? by the Bollettieri Camp "Serve Doctor", Pat Dougherty:
Main point: You need to "aim your chest at the ball" more - do this by bending more from the knees with the heels well off the court as you get into your trophy position:
The feeling you will have is more like doing a squat rather than just bending your knees. By that, it will feel like you are lowering your whole body weight down.
To maintain your balance, keep your tossing arm pointed straight up as long as possible.
To maintain your balance, lower yourself continuously (never pausing), until you begin the leg push off to start the serve. [A falling body is quite stable, it is only when stopping that it would feel difficult to balance.]
When do you do this?
Check out the following sequence of Sampras:
Notice it is only after his tossing arm is straight up in pic 4 that he begins to squat down (bend his knees), bringing his heels off the ground.
Notice that as the result of this set up into his trophy pose, his chest is more aimed up at the ball at impact.
Preventing Rotator Cuff Injury. TennisOne.com Editor Jim McLennan explains some serving techniques to generate power and protect your shoulder. http://www.youtube.com/watch?v=lTRvxaBMh8s
The fact that you are falling off to the right is proof that you don't have enough shoulder over shoulder cartwheel action.
[If you did, your shoulder over shoulder cartwheel action would throw your straight into the court.]
Again, getting into the correct trophy pose with your tossing arm straight up will help you.
But you will need to let your front hip extend more out into the court in order to maintain your balance as you get lower and lower in your squat if your tossing arm is up with a steep shoulder angle.
[That is because your upper body weight being tilted to the back fence as you form the "archer's bow" means your hip has to counterweight this upper body tilt.]
You can see how Pete gets his body shaped "like a bow" very late in the above sequence in pics 7-8, just before his final trophy position.
[Will Hamilton emphasizes this in the following video: Tennis Lesson: Serve Tips: Lead with the Hip http://www.youtube.com/watch?v=HgeYmEScfgQ
Also sliding the hip forward as you get to the trophy position is a prominent feature of Nick Bollettieri-Sonic Serve.wmv http://www.youtube.com/watch?v=ajoZ0f7hw-A
You can also see how Pete has his hip forward at his trophy position in pic 1
Once set up in this trophy position, Pete demonstrates the shoulder over shoulder action that Jim McLennan describes in his Preventing Rotator Cuff video.
[And notice that doing this shoulder over shoulder cartwheel motion propels Pete forward, not falling off to the side as you are doing.]
So good luck in working on your technique so you will not have an early recurrence in rotator cuff problems as you get back to tennis.
Keep doing the thrower's ten exercises throughout your tennis career to also help avoid rotator cuff problems: http://www.muhlenberg.edu/pdf/main/a...throwers10.pdf