Train all four phases of agility with your athletes. Their athleticism will quadruple. Let's train movements specific to volleyball and not just isolating muscles in the weight room. Both give you strength but one is more sport specific to volleyball. Now, back to agility.
Agility drills teach the athlete body control and awareness from the centered position.
This enables the athlete to explode in any direction on the volleyball court. There are four phases of agility. We need to teach the ability to stand, walk, and stop in a balanced manner. Focus on the athlete's center of gravity, their posture, and their proper foot placement. A few minutes of practice a couple of times a week early in the season can greatly enhance improvement in balance.