"The help can't get beaten." Defense needs five engaged players. Everyone gets beat; everyone helps. You can't help or rotate unless you see both your assignment and the ball. "See both." The ball scores.
Teams like spread offense, Horns, and 1-4 High offense because they create problems for the help.
Help and rotation are essential to conventional execution but also for defensive adjustments like trapping (blitzing) or run and jump (trap and go) defenses. Understanding takes hard work.
I know that if x3 gets beaten, that x5 will help to stop the direct drive. I'm not yet sure x2 will drop to help the helper. That's second order thinking. Sometimes she will; sometimes not. Intention and obstacle. Don't say, "my guy didn't score." Don't do your own thing; do our thing.
How can I teach defensive rotation better?
Create an expectation of execution. "But it's hard; I'm in a mismatch." Get past hard.
We don't double the post across. Never. I saw a championship game lost in part because x3 didn't rotate (left) creating THREE layups. Help the helper.
Drill better. We all use SHELL DRILL to teach rotation. Protect the basket (no penetration); protect the red zone (take away blocks and elbows). Add 'disadvantage' (above) to enhance the drill.
Steal other coaches' lessons. Coach Jim Huber shares an excellent help and recovery drill.
BasketballforCoaches has clear diagrams to share with players.
Rotation versus drive from the top against spread offense.
Rotation from wing on baseline drive against spread offense.
Via Seth Weakly, FIBA. Take away the "obvious" pass.
Defense means executing together. Help, rotate, and recover together.
Lagniappe:
Bring energy. Talk. Inspire. "Great shooting teams are great passing teams."