What are the real mechanical precursors of pitcher injury? And what is the real lesson of Mark Prior's injury history?
Pitching mechanics are a bit like long-snappers in football, in the sense that we hear about them only when something goes horribly wrong. Mechanics rarely enter the discussion until a pitcher gets hurt, but when an ace succumbs to injury, the village folk grab their torches and pitchforks to go on the hunt for blame.
Experience has taught me that there is rarely an isolated cause for a pitcher's injury, with confounding variables that include mechanics, conditioning, workloads, genetics, and plain old luck. The pitching delivery is a high-performance machine, with a multitude of moving parts that must work efficiently in concert for the system to perform at peak levels, and any weak link in the system can lead to a breakdown.
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PAP^3 is the name for the new system for measuring pitcher abuse via pitch counts introduced in Baseball Prospectus 2001. Though it shares a similar name and goal with a system previously introduced by Rany Jazayerli, it was developed independently, and replaces the older system.
Before claiming any success for any measure in predicting injury, we must fundamentally recognize that any PAP-style metric will be positively correlated with raw pitch counts. Pitchers with high pitch count totals will tend to have high PAP totals. If a PAP function provides no additional insight into which pitchers will be injured that pitch count totals alone, there is no reason to add the added complexity of a PAP system to our sabermetric arsenal.
There are two related effects we are interested in studying. The original intent of PAP was to ascertain whether a pitcher is at risk of injury or permanent reduction in effectiveness due to repeated overwork. And in particular, does PAP (or any similar formula) provide more insight into that risk that simple pitch counts alone?
It has now been more than two years since we created Pitcher Abuse Points
to standardize the measurement of pitcher workloads. By and large, we have
been more successful at that goal than we had any reason to expect. Some
people in baseball now agree with the notion that limiting pitch counts in
an attempt to keep pitchers healthy is one of the most important topics in
baseball. Then again, many more people think we're full of crap. Or, to
quote Bruce Jenkins of the San Francisco Chronicle:
Two years ago, when we first introduced Pitcher Abuse Points, pitch counts
were still shrouded in a veil of mystery. They were available, mind you,
but they were squirreled away at the bottom of box scores, and rarely
ventured from their hiding place to appear in game summaries or in
televised accounts of the game. Columnists never brought them to our
attention. Livan Hernandez could throw 140 pitches in utter obscurity.
Today, ESPN tracks Rick Ankiel's pitch counts the way CNBC tracks
As teams close in on the 100-game mark, enough pitches have been thrown and
enough starts have been made that we can begin to draw significant
conclusions from the
Pitcher Abuse Points
data. But before we get to that, here's a demonstration of how PAP differs
from looking at average pitch count totals:
Baseball Prospectus introduced Pitcher Abuse Points
last summer as an attempt to measure the workloads of
starting pitchers. Briefly, the system is based on the premise that each
pitch above a certain threshold is incrementally more damaging than the
last, with the damage growing more severe as more pitches are thrown. Our
threshold is 100 pitches; beyond that, a pitcher "earns" one
point each for pitches 101-110, two points each for pitches 111-120, and so
For more on the system, please check the
original PAP introduction