A 1-3-1 zone utilizes one player in the front, three players in the middle, and one player in the back. This is a defense played in the half court and the player at the top is usually the point guard with the other guard or shooting guard playing down low. The three bigger players including the center and forwards play in the middle with the center usually in the middle.
The top of the zone is sometimes referred to as the "chaser" who covers a lot of space trying to create turnovers and stop the ball from moving from one side of the court to the other. The players in the middle are sometimes also known as the "wings" of the zone. Their main goal is to create as many traps and force as many turnovers as possible. The center who usually plays in the middle has to keep the post as clogged up as possible to keep teams from getting easy opportunities inside. Finally, the bottom player is also known as the "warrior" as he must chase from corner to corner while also handling some post defense too.
The 1-3-1 Zone has a few different benefits including its versatility. To be effective a team does not have to have size or speed, just effort and good communication making it a good defense for teams without size. It also limits shooting teams by pressuring well along the three point line while also limiting the inside if done correctly. Passing lanes are also limited because of the constant motion of defenders at all times moving while the ball moves.
There are two problems spots in a 1-3-1 Zone: the corner and the post. No matter the talent of the warrior the corner will get open shots that can become a problem if made consistently. Also, his lack of size down low could give up some easy baskets if the defense isn't played perfectly. A lack of defensive aggression and effort can also make this defense also worthless as the effort causes many turnovers. Overall, the 1-3-1 zone can be effective in limiting all types of shots and a good defense to use across multiple levels of basketball.