The defensive progression
A blog article provides a useful progression to think about defending in volleyball, though there are some fuzzy points in the systems side.
Tag
volleyball defensive system
Understand the limits of heat mapping
A fellow volleyball coach highlights a weakness of heat mapping to help decide what type of defense you play
How do I make my team strong in defense?
Making your team strong in defense generally means addressing four primary areas of focus - blocking, system, digging, and mentality