Sometimes, it's best not to be straight forward. Just as water has no absolute Position, the Strategy has no absolute Direction. When an attacker is going on goal, the first thing a defender should do is slow him down. Third, he should prevent or interfere with the shot. Notice, there were no points that say tackle the ball.
D plays a long ball out to A and closes down the ball.
A receives and attempts to beat D and get a shot on goal. D is only allowed to block the shot, not tackle. Stop play after a few seconds if the defender is able to stop the attacker's momentum. Defender should have quick and constantly moving feet. The feet should never cross.