An Exploration of Pitch Type Value

Have you ever wondered who has the best fastball in the majors? What about those arguments at the water cooler over who has the better curveball –Saint Louis Cardinals’ Adam Wainwright or Los Angeles Dodgers’ Clayton Kershaw? Thankfully, there’s a stat for that.

Generally known as ‘Pitch Type Linear Weights’, these values (attempt to) answer who has been the most efficient when throwing a given pitch. Pitch value is measured using the tried and true method of run expectancy, meaning that, depending on the count, the value of the pitch goes either up or down depending on the run environment.

Let’s go into the concept a bit further. We will use an example of Wainwright facing off against Yasiel Puig with the count at 0-0; obviously, the run value of the at-bat starts at zero as no pitches have been thrown yet. Wainwright starts off with a fastball that Puig takes for a strike. The value to Wainwright for throwing that strike (or wFB) according to run expectancy is .04. Depending on how successful Wainwright has been with his fastball through the season, his fastball value will increase for that pitch. His next offering to Puig is a curveball that falls outside of the strike zone and the count moves to 1-1. His fastball value will not change, but his curveball value will drop according to the run environment.

Still with me? Good.

Over time, these values accumulate into ‘weighted’ metrics–wFB for fastballs, wCB for curveballs, wCH for a changeup and, well, you get the picture. Let’s take a look at the data below, which shows the top five wFB for the 2014 season.

As you can see, Cueto had the most effective fastball in the majors in 2014. His 22.0 wFB falls on the high end of the value spectrum. The top pitch value typically teeters around 20.0, while the lowest hover around -20.0. An average pitch–or one that has caused neither harm nor good–is zero. For what it is worth, Chris Archer of the Tampa Bay Rays had his wFB fall at exactly 0.0 in 2014.

So what does this mean? That Cueto is the best fastball pitcher in the majors? Not exactly.

wFB takes into account every single fastball thrown with no discrepancy. A pitcher who throws mainly fastballs or curveballs stands a better chance of producing a high (or a low) wFB or wCB simply because its been used more. To elaborate, a reliever like the Cincinnati Reds’ Aroldis Chapman is going to increase his tendency for a high/low fastball total because that is the pitch he primarily throws. On the other hand, a pitcher who has five different pitches to work with may see his value on certain pitches closer to the mean.

This is where we can take it one step further. We have the option of quantifying the value of a pitch to a ‘per 100 pitches’ score known as wFB/C, wCH/C, etc. These values have a variable that allows a pitcher who throws 500 fastballs to be ‘fairly’ compared to a pitcher that may only throw 300.

Using the above information, we can see a slight difference in the top five fastball pitchers for the 2014 season:

Using the data scaled to ‘per 100 pitches’, Cueto is tied with Kershaw at a 1.27 wFB/C. This means that if they both throw 100 fastballs–perhaps in the same run environment–the pitch would be equally as effective.

OK, now that we have this concept understood, we must now apply good ol’ context.

First, this stat is not predictive of future performance. It only gives us information about what has already happened and should not be relied upon in terms of consistency. Maybe one day Masahiro Tanaka has Derek Jeter playing behind him one start but the next day it is Brendan Ryan. Ryan is by far the better defender and is more likely to save a ground ball up the middle from becoming a base hit and lowering the value of whatever pitch Tanaka had thrown.

Another factor to consider is a pitcher like the Atlanta Braves’ Julio Teheran, who has Andrelton Simmons playing behind him. Chances are he may have a better score on a given pitch because almost nothing gets past Simmons for a base hit. While the impact on value may end up being slight, you have to consider Atlanta’s pitchers having an advantage over other pitching staffs due to an elite middle infield.

So, the next time average ‘Joe Baseballfan’ approaches you to tell you how much better Wainwright’s fastball is than Kershaw’s (we have learned that it is not), you are able to discredit that point by using the linear weights on pitch types.

Want an explanation of another stat? Check out our Saber Glossary.

• Published on 03/06/2015 at 6:47 AM EDT
• Last updated on 03/06/2015 at 6:47 AM EDT