In the rules of the tennis match, each player has only two serve opportunities when serving, if the first serve error.

When the second serve is completed, it must be completed within a limited time. If the caddy is called to get the ball, it will inevitably delay the time and affect the smoothness of the game.

So many female players will carry a ball with them, because the traditional ball suit has no pockets, it can only be inserted into the side of the shorts in the skirt.