Frontline defenders must be able to defend wing perimeter players (as is the case in the 1-1-3);
A very quick guard is required, who plays the back of the zone and is responsible for coverage from one corner to the other;
Preferably the guard that is to play the back of the zone, should be a relatively tall guard, as they will at times have responsibility to defend in the low post.

An advantage of the 1-3-1 Match Up compared to the 1-1-3 Match Up, is that it provides better coverage on perimeter shooters, particularly at the wing.

Initial Alignment for 1-3-1

The “up guard” is responsible for the middle of the court, and for influencing the ball to one side. The “back guard” plays as the last line of the defence and covers from one corner to the other.

x3 and x4 retain responsibility to defend the wing perimeter players, and have less distance to cover than in the 1-1-3.

x5 is responsible for stopping any penetration into the keyway.

The reason x5 has responsibility to defend dribble penetration, is that if x4 steps in to stop the drive, it will lead to 3 being open, which negates the advantage of the zone (which is coverage on perimeter shooters).

On pass to the wing, rules from the 1-1-3 apply:

Frontline player (x3) defends the wing player;
Up guard rotates to deny the high post
Front line player (x5) rotates to be in front of any low post player
X4 rotates to a help position.

The back guard (x2) moves toward the corner, but remains in the keyway. If the player in the corner is a very good shooter, x2 can hedge closer.

When the ball is passed into the corner, x2 moves to defend the player. x5 moves to front the low post player, and x4 remains in a help position behind the post player.

x3 can hedge down toward the low post, but has primary responsibility to defend the wing.

Defending the Dribble

On any dribble penetration from the corner, the defender in the low post area moves to stop the dribbler.

x3 may hedge to the dribbler, but ultimately must keep the wing player in sight and be prepared to guard that position.

Similarly, any dribble penetration from the point position, is defended by x5 stopping the dribbler from getting into the key.

The back guard (x2) also moves across the key, to be closer to any perimeter shooter in the keyway.

Where there is a low post player, x2 may rotate to deny any pass from a penetration dribbler to the low post player.

Trapping from 1-3-1

A player in the corner can also be “trapped” by the perimeter defender following the pass down.

Alternatively, x3 can deny any return pass to the wing, which means that all close passes are denied.

Whatever Match Up defence a team wants to employ, it will only be successful if:

Defenders can defend a perimeter player to stop them from passing or dribbling;
Defenders “fly with the ball”, moving as the pass is made;
The defenders communicate with each other.