Being able to play on ball defense takes good technique and also the ability to move quickly laterally in either direction. To be good at these things you have to be willing to put in the time working on them. This defensive basketball drill is going to work on being able to guard a live dribble, and is also going to work on learning to compete. There is not help defense, so that means the defender is going to be put under a spotlight. Everyone will be able to see what players are able to guard the dribble, and which ones are not quite there yet. This basketball drill is also able to accommodate a larger group of players as well, so it is great for practice settings with the whole team.
Make sure that you are watching the footwork and technique of the defensive player. If they are practicing bad habits in live defense, you may want to switch to a different defensive drill that works more on the players individual technique. Don't allow bad habits to creep into a players defense.