Three months ago I was almost hit by a car while riding my road bike. I had to hit the curb to avoid being struck. It fractured my ankle in 2 spots. It has taken three months to recover and I'm still doing rehab!
 
I could not drive or walk. Very frustrating. Once the bones healed, I started rehabbing it. I could not drive to the gym so I did all the rehab at home. I actually quit my gym after almost 20 years.
 
As my ankle got where I could bear weight and walk, I continued my rehabilitation. I would get up early A.M., walk my dog for 1 1/2 miles, then come home and do a series of exercises; three sets of 20 crunches, three sets of 20 pushups, three sets of 20 dips, two sets of 10 pull-ups on a chin up bar that sets on the door. I do this everyday now, plus I try to ride my bike 100 miles a week. The biking actually does not hurt the ankle because your weight is on your seat not your legs.
 
After everything got better I did not rejoin the gym, I have created my own gym at home. My message to you is find something that you can do that is convenient, not costly and not too time consuming. If you are a tennis player try to do exercises that support your game. Maybe it's walking or stretching, light weight lifting or yoga. Just find something that works for you and "just do it!" Life is about maintenance! Keep it up!
 
Good luck on the courts!