(This is the first of a 3-part series that I’ll be running on the TwinsCentric blog and at TwinsGeek.com. Part 2 will be published on Memorial Day and Part 3 on June 3rd.)

Let’s be honest: for the first one hundred years or so of major league baseball, the players were chattel. That’s the biggest reason that starting pitchers were allowed to throw until their arms fell off. Management didn’t really give a damn if they fell off or not.
That’s also why things have changed. With the introduction of guaranteed contracts, a fragile arm can sink an entire front office. (Just ask Omar Minaya next fall.) So teams, coaches, agents and certainly players are looking for a way to protect those investments. Pitch counts seemed like a good place to start. And 100 is such a nice round number.
But don’t make the mistake of thinking there is any science behind it. Or at least that it isn’t paper thin. The current wisdom that 100 pitches is some kind of limit is an overly simplified interpretation of very specific studies that weren’t afraid to point out their own limitations.
The most commonly quoted - and arguably the most comprehensive - research on pitching abuse was a pair of essays in the 2001 edition of Baseball Prospectus. The first is called “Re-Thinking Pitcher Abuse” by Rany Jazayerli, which gives a brief history of his attempts at studying pitching abuse and summarizes a new measurement called PAP3. The second is “Analyzing PAP,” written by Jazayerli and Keith Woolner, which details the study that led them to develop the new measurement.
Both essays are very candid about what they found and what their limitations are, mostly without an ax to grind. Unfortunately, the measurements they created have been misinterpreted and oversimplified to become some deranged gospel of truth that doesn’t exist. So let’s take a look at what we REALLY know about pitch counts from those essays. 


Re-thinking Pitcher Abuse Essay

Jayazerli introduces both essays by explaining his original theory: that all pitches are not created equal. In particular, pitches thrown later in a game, once the arm is tired, are more damaging than those thrown earlier in a game.
When Jayazerli had proposed that idea earlier, he also devised a statistic to try and measure it called Pitching Abuse Points, or PAP. The original idea was that the first 10 pitches over 100 would be worth one point each. The next 10, two points each. The next 10, three points each, and so on. The more points, the worse the risk to the pitcher.
(In the later essay, Jayazerli says he chose 100 as a starting point because of research dating back to Craig Wright’s The Diamond Appraised, which suggested the 100-pitch limit for developing pitchers. I’m afraid I haven’t procured a copy of that book to see exactly where it came from.)
Jazayerli had thrown out this statistic as a starting point, but BaseballProspectus.com was exploding in popularity at that time, and he noted that a strange thing happened:
“And for two years, I have tried to use PAP as a framework in which to center the ongoing discussion of pitcher usage. In the process, though, PAP became more than a framework for measurement; it became the standard for measurement. Which it was never intended to do.”
Jazayerli then points out that he had never found any evidence that this PAP score is tied to injuries. He explains that it is a very difficult thing to measure because of all the confounding factors. So he enlisted Keith Woolner’s help and they conducted another study (detailed in the second essay) which resulted in a new measure called PAP3.
PAP3 was similar to PAP except that the points increase exponentially once you get over 100 pitches. Basically, you cube the number of pitches over 100, so 105 pitches would be 5^3 or 125 points. But 110 pitches would be 10^3 or 1000 points. And 120 pitches would be 20^3 or 8000 points.
You can see, that creates some very scary looking numbers in a hurry. However, the standard for what was truly damaging was also raised considerably. So they also included a table which listed the pitch counts along with their risk. Anything below 105 pitches was “virtually none.” Anything under 122 pitches was “moderate” and anything over 133 pitches was “severe.”
So let’s review what this essay just said. First, it explains that there was never any evidence that a previous metric (PAP) was ever valid. It pushes any significant risk in pitch counts up to 120+ pitches. And finally it presents a new metric (PAP3) for evaluating pitcher risk.
Of course, the evidence that PAP3 is any better than it's predecessor is in the second essay. We’ll start evaluating that in Part 2 on Monday. 
I really, really, really cannot believe that I haven’t covered this next item yet. I’ve just been distracted by some life stuff. Many of you may have heard that one of the TwinsCentrick authors, Parker Hageman, has been designing some t-shirts for Twins fans. His initial one is a “Thome is my Homey” t-shirt and the first batch already sold out, but they’ve ordered a second batch. You know you’re going to want to rock this shirt at your next Twins game, so get it now, because I don’t think there will be a third batch.