The Importance of Game Like Random Blocking

We think as far as serving is concerned in our gym, we can't make it any better. Stretching doesn't help you keep from getting injured. And so we don't do stretching in our practices. None. But if I have a club team, say they're 14s and I only have eight players don't need to spend time stretching and jogging and we can't just play the whole time. So then what do I do? How can I play game like if I don't have 12 people? That's the thing I was worried about when we were talking about whole versus part practice. Well, I think there is some confusion on the semantics of what this looks like