Tennis movement is highly situation specific and is performed in a reactive environment. This irregularity of movement requires both general movement training, but more importantly tennis-specific movement training. The need to continually respond to situations requires a fine understanding of the athlete’s game style, strategy, movement strengths and weakness. Movement for tennis is both simple and complex.
A great analysis of tennis that should allow you to use the specificity training principle in your off court training. Short sharp high intensity intervals with slightly longer rest breaks seem to be the fix. Also lots of direction changes, especially laterally.