There’s another article of mine up on Baseball Analysts about how the strike zone expands/contracts as the count changes and how different some pitchers take advantage of it.
“Ideally, a pitcher is going to try and get ahead in the count and when this happens the pitcher has effectively “expanded the strike zone” since the batter is now on the defensive and will be more prone to chase pitches outside the strike zone. Conversely, when a pitcher is behind in the count, a batter will be less prone to chasing bad pitches. Looking at OSwing by count this becomes fairly evident.”
You can find the rest of the article here: Expanding the Strike Zone
David Appelman is the creator of FanGraphs.