Pitch Type Linear Weights
Description:
The Pitch Type Linear Weights (“Pitch Values”) section on FanGraphs attempts to answer the question, “Which pitch is a pitcher’s best weapon?” How likely is a team to score before the pitcher throws his first pitch? Now how likely are they to score after the pitch? These changes in run expectancy between an 0-0 count and a 0-1 or 1-0 count are obviously very small, but when added up over the course of the season, you can get an idea of which pitch typically yields good results to a pitcher. If one pitch is getting hit especially hard or a pitcher can’t locate one pitch for a strike, these problems will show up using Pitch Type Linear Weights. And if a pitcher gets lots of strikes and outs with a specific pitch, this success will also show up.
On FanGraphs, you’ll notice that there are two different types of Pitch Type Linear Weights: total runs by pitch (which is shown as wFB, wSL, wCB, etc.) and standardized runs by pitch (shown as wFB/C, wSL/C, wCB/C, etc.). The first category is the total runs that a pitcher has saved using that pitch; however, it is tough to compare these total numbers since pitchers throw different amounts of each pitch. The second category corrects for this, standardizing the values on a “per 100 pitch” basis. In other words, when you see wFB/C, that represents the amount of runs that pitcher saved with their fastball over the course off 100 fastballs thrown.
Context:
A Pitch Type Linear Weights score of 0 is neutral, with negative scores being bad and positive scores being good. Last year, the highest wFB for any player was Josh Johnson’s 21.5, while the lowest was Carl Pavano’s -23.6. For comparison, the highest wFB/C for any player was 2.01 by Chris Carpenter and the lowest was -1.37 by Carl Pavano.
Things to Remember:
- This is a relatively new statistic at FanGraphs and I am uncertain to what extent Pitch Type Linear Weights has predictive power. At the very least, they can show you what pitches a pitcher has had success with in the past, but can you expect these pitches to remain dominant/poor in the future? That’s a tricky question and depends on the pitcher’s mechanics, health, and how they adjust to batter adjustments. I’d be very careful using this statistic to look ahead into the future.
- Pitch Type Linear Weights can also be used to evaluate hitters and what pitches they have had most success against in the past.
Links for Further Reading:
