A professional tennis player can be referred to as a tennis pro, a tennis star, a tennis athlete, or a tennis champion. Alternatively, they could be called a tennis expert, a tennis ace, or a tennis specialist. They may also be known as a tennis performer or a tennis practitioner. In some contexts, they could be labeled as a tennis professional or a tennis master. Additionally, they might be considered a tennis virtuoso, a tennis prodigy, or a tennis sensation. Ultimately, there are many ways to describe an individual who earns a living by playing tennis at a high level, and the specific terminology used may vary based on the speaker, the audience, and the circumstances.