So when I look at the Play/Game Log.

Next to the defense that was called for that play, it will show whether the defense keyed on the run or pass or showing nothing at all.

When it shows the key (or nothing)....what is the origin? Was it set by the opponents owner in game planning? Or was it the "AI" coaches?

If nothing is shown...was that just set to neutral in the game planning section?

Thanks.

Nothing is Neutral (50%run/pass) reaction
Run is when you chose the right defense for the called play and AI made it key run
Same for pass

It's based on the 'run pass' key in your defensive game planning, but if the offense is overusing the run or pass the AI will start to key correctly automatically, which is why you might see it if you have all neutral in your game planning.