Player throws up the ball for himself via underhand, technical throwing motion. Player has 1 leg in front, arms extended, slightly to the side of the body and throws up and catches.
Now player throws ball up the same way and then keys it and then catches.
2 rows. Players stand at the back of the field with ball. Trainers stand at the net. Player throws via underhand throw to trainer. Trainer fends off and then throws the ball to the same player. Player tests the ball directly back to the trainer and tries to get to the trainer faster than the ball.
Idem, only now the player doesn't hit back directly but hits for himself twice and catches the ball and joins the back of the line again.