One of my favorite defenses in basketball is the 2-1-2 zone. I often call it "X" because of how the players set up. If it's done well, it makes it very difficult for an opposing team to score in the paint.
This article discusses when to use it, how to set up for it, the roles of the different players, and the defense's weaknesses.
Using the Basketball 2-1-2 Zone Defense
The 2-1-2 defense makes it difficult for the other team to score in the paint and around the key. It's a great defense to use against teams that have that type of offense as their strength.
The figure below shows how defenders should set up in the 2-1-2 defense. Players 1 and 2 set up near the top of the key on either side of the free-throw line. Players 3 and 4 set up near the low post on either side of the basket. Player 5 sets up in the middle. Players 1 and 2 need to be fast and have superior ball-handling skills. Players 3 and 4 should be excellent rebounders. Player 5 should be a big, aggressive player.
Players 1 and 2 meet the point guard, keep the ball from entering the top of the key and prevent it from being passed. Players 3 and 4 keep the ball from entering the low post. They also go out and meet the ball when it's in front of them. Player 5 keeps the ball from getting into the paint.
This is a simplified explanation of roles. In reality, the players constantly shift in response to the location of the ball and what the offense is doing. Below are two common examples of how this works.
The ball is up high
In the figure below, the ball has been passed to offensive player 2 on the wing. Defensive players 2 and 3 move to trap him. As that happens, player 1 shifts to cover 2's area of responsibility, 5 shifts over to cover 3's area of responsibility, and 4 shifts over halfway to be able to react.
If the defense is doing its job, offensive player 2 will have difficulty passing the ball or moving without turning the ball over. Even if the ball can be passed, defensive players 1 and 5 are covering a pass away and can either prevent the pass or the penetration. Defensive player 4 is ready should the pass go down low.
The ball is down low
In the next figure, the ball has been passed down low to offensive player 4. In this situation, defensive player 4 moves over to contain. Defensive player 3 shifts over to cover 4's area of responsibility. Defensive player 1 shifts over and down to prevent passes and penetration into the key. Defensive player 2 shifts over to cover 1's area of responsibility. Defensive player 5 stays in place and is ready to react.
If everyone does his job, defensive player 4 covers the ball down low. Defensive players 3 and 4 prevent any movement toward the paint. Defensive players 1 and 2 are able to disrupt any pass from offensive player 4. Defensive player 5 is ready to react to any movement towards the paint.
For the 2-1-2 defense to work, players have to cover their areas of responsibility. An example of how not to play the 2-1-2 defense is shown in the figure below. The ball has been passed to offensive player 2. Instead of covering his area, defensive player 4 runs across the court and go after the ball, leaving offensive players 3 and 4 completely open. If the ball can be quickly passed there, they have an easy basket because of defensive player 4's mistake.
Every zone defense has weaknesses. Though the 2-1-2 is great at preventing scoring in the paint and around the key, it is not a good defense against a team that shoots well from the outside. It also does not do a good job at preventing passes to the wings. So if you are facing a team that can score from outside, a man-to-man defense will be a better option.