If you're sick of answering, “Was that ball mine?” consider running this defensive drill that works on communication, defensive pursuit, anticipation, and teamwork. Jen Dejarld, the head coach at Mother McAuley High School, uses this drill weekly with her team and provides tips for implementation in this video.
To set up this drill, 2 players split the court and a coach stands at the net. The coach initiates a ball, and players have 2 contacts to get the ball back to the coach. The players stay on the court until they reach a set number of completions. If a ball touches the ground without effort, they lose all of their completions. The final catch: there's no out of bounds and the coach may enter the ball anywhere.
Dejarld starts out by entering easier balls and gradually advances to more difficult balls. To modify the drill, the coach can allow for a third contact if the ball is entered ridiculously out of bounds.