Josh "Air Yards" Hermsmeyer wrote this piece for FiveThirtyEight showing that play-action passes do not lose their effectiveness the more often teams call them in a game. What's more interesting than the conclusion is Hermsmeyer's methodology -- using the NFL's Next Gen tracking data, he followed middle linebackers and tracked how far they moved in pursuit of running backs who they thought had the ball. It's cutting-edge analysis that looks not just at how play-action works, but why.