As the excellent Performance Specialist Allistair McCaw says you have to “connect before you direct”.

If you start out making changes to a players game before you have gained their trust they are likely not to buy into your idea or listen as carefully, which will most certainly slow down their speed of learning. Then as a coach you might confuse their speed of learning/talent with the degree of trust that you have gained with the specific player.

If you can get the person, the development of the Tennis Player is easy.

If you want an interested player, you need to be interested in your player.
1) Find shared interests outside of tennis
2) Figure out where the player is born & raised
3) Get to know how to make them laugh