Thursday, March 04, 2010
The influence of batters’ expectations on pitch perceptionPosted by Craig Glaser
Hi everyone. This is my first post on The Hardball Times Live and I’m really excited to have to opportunity to post here. I hope you enjoy my work. You can find more of my original research at my personal site.
What we’re going to look at today is the relationship between percentage of pitches on a certain count and batting eye by pitch type. You can read more about batting eye at my site but to summarize - it is a measure of how good the batter is at judging whether a pitch is in the strike zone.
Batters are obviously much less concerned with taking a strike when they have less than two strikes on them - and may choose not to swing at pitches which they know are strikes in these counts. Therefore looking at batting eye on most counts is an imperfect measure. For this reason we are going to look only at two strike counts for this analysis.
Unfortunately this gives us a mere four data points per pitch type, which means that the correlations I’m going to show you are based on a very limited number of points. On the plus side each point represents a few thousand pitches. Additionally, while this data is for the 2008 season, the numbers look very similar for 2009. I have also done a bit of follow-up analysis which will allow me to look at more of the points at the same time.
Let's take a moment and think about what we might see in this analysis. I came up with a couple of different theories.
-You might suspect these measures are completely unrelated. After all a curveball is a curveball regardless of count and the batter should be consistent in their ability to tell if it’s going to be a ball or a strike.
-Perhaps pitchers can outsmart batters and throw pitches which the batters are not expecting.
Since I’m writing the article you can pretty much rule out the first theory and while some pitchers might be able keep batters off balance it doesn’t seem to be the case when we average over the league.
You might now conclude that the two measures are directly related - that the more frequently a type of pitch is thrown on a specific count the more a batter will be expecting that pitch type and the better they will read it. You’d be right – with one exception. Check it out.
We see that this strong positive correlation between percentage of pitches and batting eye exists for three of the four main pitch types. Batters seem to be better at reading fastballs, curveballs and sliders on counts where those pitches are more likely to be thrown. But what’s up with the change-up?
The change-up is generally thrown as a complement to a fastball. After seeing this data I thought that correlating batting eye on change-ups with percentage of fastballs thrown might be interesting. Here we see a pretty strong negative correlation.
I want to include one caveat here. Batting eye on change-ups also correlates strongly with percentage of sliders and curveballs thrown. In fact these correlations are a bit stronger. Comparing change-ups to fastballs makes the most sense to me intuitively, but the batter could just be looking for more off-speed pitches which might help them pick up change-ups.
Overall I think that there is ample evidence to support the following conclusions:
-Batters are better at judging whether a pitch will be a ball or strike on counts where they expect that type of pitch to be thrown.
-Batters do a good job of anticipating what percentage of each pitch type will be thrown on a specific count.
The one exception to these rules is the change-up, which batters seem to be better at picking up when they expect less fastballs (and more off-speed pitches.)
I'm really looking forward to delving deeper into baseball and the tendencies and strategies behind it. I hope you'll enjoy reading my posts as much as I'll enjoy writing them.
Read more of Craig's work on his website Sabometrics