compiles and rates a player's efficiency based on the combination of shooting, rebounding, assists, and turnovers?

Knell is shown to have shot at a higher level than others, but I believe he was (a) a net liability on defense and (b) not a net positive if we factored in his opposing players offensive success AND rebounds AND turnovers.

Spot up shooting? Probably but other aspects he fell short. That is my impression but I haven't analyzed the data.

My impression was you didn't want Knell guarding a great offensive player, he didn't drive to the basketball well and couldn't create his own shot.