The International Soccer Coaches Association

This practice will improve each players "one on one" defending skills.

The practice starts with the first attacker in-line. The attacker
places a firm shot for the goalkeeper to save (they are not trying to score). When the goalkeeper catches the ball he then throws it to one of the wide defenders. The attacker turns and receives a first time pass from the defender. After receiving the pass, the attacker has to try and beat the defender and score in the wide goal. The defender must try to prevent the attacker from scoring.
When the attack is ended, the attacker then becomes the next defender, and the defender joins the line of attackers.