Beard's substitution patterns

I must admit that on the surface, Coach Beard's substitution patterns seem illogical to me. It appears that we have lower-tier players on the court far too much for the team's performance to be at its optimum level. However, there are factors other than those that are most readily apparent. In the first place, he knows the players, and he knows what motivates them, and how quickly they tire or lose focus. He seems to be a good motivator, and playing time may have a lot to do with that. So, while it puzzles me, I have to assume there is a logical reason to what he does and fits his overall scheme of things.