Just a word of caution.
Plyometrics place a lot of strain on the body.
If you have the time, building a base of strength can better prepare your tendons, ligaments and joints to withstand the jarrring effects of plyometrics plus playing tennis:
"Unlike many sports, tennis demands several different types of strength... in particular muscular endurance and explosive power. And before these can be developed to optimal levels, the athlete needs to first develop good foundational and maximum strength.
If you try and train for every type of strength at once you'll end up with very little of anything - except fatigue!
So the best method is to focus on one type of strength in each separate phase. That way, you can easily maintain your gains during the competitive season.
Phase 1 - Foundational Tennis Strength Training
The objective of this 6 week phase is to build a solid base on which you build more intense, more tennis-specific fitness later.
Like all competitive sports, tennis places uneven demands on the body. You swing with one arm and one side of the body. Certain muscle groups are overworked while others are neglected.
Infamous over-use injuries like tennis elbow and damage to the rotator cuff muscles are less likely to occur in a balanced physique.
So our goal during this first phase is to prepare the ligaments, tendons and connective tissue for more strenuous activity to follow.
Phase 2 - Maximum Tennis Strength Training
Now that you have a solid and well-rounded base of strength, you can move on to more intense sessions.
The objective of this 6 week phase is to build high levels of maximum strength. What exactly is maximum strength?
It's simply the amount of force you can apply in one single, voluntary contraction.
Why is maximum strength important to tennis players?
On it's own it isn't. But power, which can be a defining factor in the game, is a product of speed AND strength.
The more maximum strength you have the greater your potential for power.
Phase 3 - Convert to Power & Strength Endurance
On its own maximal strength is not much use for the tennis player. Unless you can apply a high proportion of that strength quickly (explosive power) and over a prolonged period (muscular endurance), you won't see a great deal of improvement on the court.
It's during this phase that more and more tennis-specific exercises are incorporated... exercises that mirror the movement patterns of the game as closely as possible.
To develop explosive power, it's crucial that exercises are performed explosively. As a result, the resistances must be reduced. Lifting heavy weights near one rep max, won't allow the neural adaptations to take place that occur with quick, dynamic movement."
You may want to check out the above link for a specific work out program that will take you through the preliminary phases up to a plyometric program.