The Interaction of Speed and Location on Fastball Success
One thing I have been interested in is how pitch location and speed interact. Are there pitch locations where it is especially important for a fastball to be fast (up in the zone) and others where a slow fastball does just as well as a fast one (the outside edge)? We have some assumptions going in, but I wanted to see what the data have to say. I am going to restrict my attention here to four-seam fastballs.
We know about fastball success by speed. Josh Kalk showed the faster the better for fastballs, not too surprising. And Max Marchi gave us the success of a fastball by location. For horizontal location you get a 'W' shaped graph. That is pitches outside the zone and down the middle of the plate result in higher run outcomes (the outer branches and middle of the 'W'), while pitches on the edge of the zone result in lower run outcomes.
To see how these two factors interacted I plotted fastball success by horizontal location for three groups of four-seam fastballs: all fastballs, those over 95 mph and those under 87.5 mph. The result below is just for those pitched to RHBs, so the inside is negative numbers and outside is positive numbers. The error bars are the shaded bands. The run value is the change in run expectancy so negative is better for the pitcher.
Outside of the zone there is no difference between the three groups. So a batter's ability to lay off a fastball inside or outside the zone is, seemingly, unaffected by the pitch speed.
The difference is pitches over the plate. With the largest difference in the middle of the plate. The slower the pitch the more pronounced the 'W', so the more penalty for hitting the fat of the plate. Pitches on the edges of the zone are fairly close, slow and average fastballs do almost as well as fast ones.
Let's look at the same pattern for vertical location. I normalized the zone so that each batter had the average top and bottom of the zone, which are indicated. I also flipped the graph so that the dependent variable (pitch height) is along the vertical axis.
Here pitch speed can cover up an inability to hit the zone, but just above the strike zone. Fast fastballs above the zone do much better than slow or average fastballs. This difference between fast and average is maintained through the top third of the zone, and between fast and slow through all but the bottom fifth of the zone. For fastballs low in the zone there is no difference based on pitch speed.
Generally we do see some interesting interactions of fastball speed and location on fastball success. A faster fastball will not save someone who cannot get the ball in the zone, but fastball speed gives a pitcher a lot of leeway to hit the fat part of the plate and pitch up in the zone.