How to Compensate for Limited Mobility (particularly when coming back from an injury)

1. Play on or inside the baseline.  There is less court to cover the closer you play into the court. Positioning may be compromised creating more difficult shots at your feet but it beats the alternative of not being able to get to a shot.
2. Develop good hands and the ability to volley from all court positions. Having the ability to control the angle face of your racquet with your wrist, hand and continental grip is the key to having success volleying from all court positions (particularly from deeper, mid-court positions). It’s important to learn how to open the face of the racquet (hitting up on the ball as necessary) to control the depth and angle of your shots. A great drill is to hit volley to volleys (working not to let the ball bounce) first from up close and then progressively from deeper and deeper court positions on the court.  (For the same reason it’s also good to learn how to hit a half-volley and how hit the ball on the rise or on the short hop).
3. Move in with each shot.  Move in slowly with each shot to cut off the angle and take advantage of your newly acquired volley and half-volley skills.
4. Stay balanced and centered.  Pay particular attention to your posture and balance. Stay centered with core stability.  Keep your head still (and centered above your hips). Avoid abrupt and sudden stops and starts.  Be careful not to lunge and reach (with your elbows out away from your body).
5. Use an open stance.  Use an open stance to better facilitate a more effortless and smoother move to the ball and recovery after the shot.
6. Get air under the ball and take pace off the ball. Hit with high net clearance and depth to buy more time.  Use spin and net clearance to slow down the pace of the ball (and the rally) and to give yourself more time to recover between shots.  Take pace off the serve to allow more time to close and/or recover. Likewise, control the tempo and flow of the match to your advantage.  Take sufficient time between points, games and sets.
7. Make your opponent(s) run.  Easier said than done but the more you can move your opponents the less likely they are in a position to make you run.
8. Anticipate.  Look for cues and tendencies to better anticipate the directional intent of your opponent’s shots.
9. Become a “Court Physics Master”.  Study the dimensions and lines of the court and net height distinctions. Learn basic angles of probability and how to position yourself to bisect angles of possible and probable outcomes. Study flight path trajectories before and after the bounce and the best footwork patterns and path angles to the ball and in recovery after the shot. Develop “that sought after by every player” court awareness and presence. Apply this knowledge to get into the best possible position before and after each shot with efficiency and the least amount of energy expenditure and effort.
10. Know when to say no to go. Following the theory of diminishing returns, recognize when and when not to exert effort and when and when not to go for the ball.

Other things to look at are your racquet and strings.  An oversize racquet may help to get more balls back in play.  A looser string pattern and lower string tension also helps to generate more power (which is important if physically you are not able to generate as much racquet head speed and/or if conditions require a more compact swing.)