4 cones spaced as a square. All four are different colours. Player starts on whistle from coach outside 3 point arc and sprints to middle of zone, turns and begins foot-fires. The coach then calls the colour of the cone. The players turns to sprint low, closes out using technique emphasised below, stays for a short period continuing to foot-fire before returning to the middle to await next colour command.

Overload player with 30 seconds (longer than any spell of defense half-court) of intensity focused on closing out smartly, quickly and with effective technique

Change angles of cones
Create more cones
Bring in chaos scenario by placing people or obstacles to get around (looking at split-line chaos)

The emphasis should be on:

staying low to sprint out - HEAD OVER HIPS OVER HEELS!!
half-way to offensive player, foot and floor contacts should become quick touches (no lunging)
To generate sideline push, inside foot should be over offensive players inside foot - prevent middle penetration
Inside hand should lead to the ball to put off quick shot
Outside hand should lead to sideline & possible deflection on pass