Offense has all kinds of counting stats that are really useful. Tons more data is collected. Defense is a different animal. For the longest time, all there was to work with was:
Who handled the ball? Did he bungle it? Did he throw it? Did he mess that up? Did the other guy catch it or muff it? Was the batter out or safe? Were any runners out or safe?
Then, we were able to keep track of where balls were hit. We were able to roughly figure how good guys were at getting to the balls around them, by combining this new data with the questions above.
Nice, but still crude.
This is going to change everything.