Today's post concerns an interesting trend in pitch distribution: "establishing the fastball". You often hear about this strategy from broadcasters, but essentially the idea is to establish that you will throw your fastball early in the game (perhaps to set hitters up in terms of timing or trajectory), and then work off of that set up to effectively mix in your other pitches.

My disclaimer here is first that I'm just looking at a few pitchers on one pitching staff that's been caught by one catcher the majority of the season. Can we capture this trend and gain some insight into pitch distribution?

Data for this project has been gathered for from every game in the 2008 season. Pitch identification has been done by the MLB Gameday Algorithm, which isn't great, but we're also looking for something that's supposed to be a very large effect, so it's possible that this won't prevent us from finding it.

To begin, I'll look at Daisuke Matsuzaka, who's fun to write about and sometimes aggrevating to watch pitch.

We'll start by dividing up "Pitch Counts" into a series of 20-pitch groupings and then looking at the relative distribution of pitch types within those groups.



You can pretty clearly see that the proportion of fastballs (plotted here in green) decreases steadily through the first 40 or so pitches, and the proportion of sliders generally increases; both of these values then level off into a relatively stable proportion for the rest of the start. Meanwhile, the relative distribution of other pitches stays essentially unchanged.

I've labeled these things here:


So, it's fairly easy to see that the pitch distribution for Daisuke, averaged across all of the games in the season, is at first biased heavily (over 60%) in favor of throwing a fastball, which steadily levels off to around 50%, and the proportion of sliders increases from less than 20% to greater than 30%.

These effects are even more dramatic when looking at what Daisuke throws on an 0-0 count:


Early in the game you have an over 80% likelihood of seeing a first pitch fastball, which decreases to (and levels off at) just above 50%. Likewise, seeing a slider on the first pitch starts at around 5% and increases to (and stablizes at) 25-30% likelihood.

Some pitch distributions, however, remain relatively unchanged. For example, if you get into a full count, in most game situations the pitch distribution is relatively equivalent (although, caveat emptor, there's a lot of variability due to small sample size):


On the other hand - and I was quite surprised by this - if you're in any 2-strike count, the pitch distribution still follows the game plan. So, early in the game he's not trying to put you away with the slider.


What does all this mean? Well, I think one thing it shows is that although a pitcher (like Daisuke) might have a relatively stable pitch distribution after some reasonable point in the game, using the aggregate pitch distribution numbers that are shown on some websites might not be such a good idea. In order to get a good idea of the real proportion of pitches, it's best to first adjust for establishing the fastball.

Let's take a look at other Red Sox pitchers to see if we can get a better handle on this. Here's Jon Lester, showing a similar trend, but with a quicker "fastball establishment":


But, the trend becomes more like Daisuke's trend if you look at only 0-0 counts:


So, again, over the first 40 pitches, the fastball is "established" and continues to lose likelihood of being thrown, while the curve and slider/cutter increase. Of course, Jon Lester throws a much larger proportion of fastballs, but the trend is still relatively apparent.

For Josh Beckett, on the other hand, we see a much more gradual decline in the relative proportion of fastballs thrown over the course of the game:


But again, this trend (40 pitches of fastball establishment) is recaptured quite nicely if we look at only 0-0 counts:


So, what have we learned? Well, it's fairly easy to see "Establishing the Fastball" as a gameplan strategy by the Red Sox staff as a whole (and not just Daisuke), and it appears to take about 40 pitches before Sox pitchers stablize into their gameplan. After that, the relative proportion of pitches remains relatively unchanged.