This is where you can hire staff members assigned to trainings, healing excepted. The level of the Training Center determines the maximum level of your training staff. The most qualified staff must be attracted enough by your infrastructure to apply. For example, under the level 4, you cannot hire a Tennis Legend.
When you wish to hire or replace a staff member, the Training Center offers you up to 6 applicants of the desired type. These applicants change after each tournament and depend from your player's overall score.