FanPost

A Simple New Way to Evaluate Pitcher Usage and Abuse: Part 1

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Photo Credit: MLB Advanced Media, LP.

Often times, especially on gamethreads, we speak of Terry Collins abusing his bullpen relievers by using some of them too often, leaving them in to pitch for too long, or both. For the most part, we have a pretty good idea of which relievers are being abused. But wouldn't it be nice if we could actually measure the extent to which a bullpen reliever (or even a starting pitcher) is being used and/or abused... you know, by putting a certain actual number on it? Well, with my simple, easy to follow system, now we can!

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I took a shot at depicting relief pitcher usage and abuse a few days ago, but something was definitely missing from that, and more work needed to be done.

I crunched the numbers for starting and relief pitchers - looking specifically at games played and pitches thrown - going all the way back to 2009; I'll spare you the complexities involved in devising my system (which requires some linear algebra and such), but basically, it works out like this:

Each pitch thrown = +1 pitch (obviously)
Each game played = +50 pitches (it worked out this way, and it actually seems pretty accurate, given the "warming up" process)
Every following day = -28 pitches (this reflects pitcher rest)

It was developed in this way, so that it's easy to follow, while also being relatively accurate. (It's designed so that anybody can keep track.) Under this system, the tally is cumulative from day to day (with the above calculations being applied as necessary), and the tally itself cannot be less than 0. From this point forward, I will refer to this tally as a pitcher's "Fatigue Index" or FI. Now, let's look at our favorite example for 2017, Hansel Robles:

Hansel Robles sample


First, some context is needed here. "FI, after" is the Fatigue Index to be used. Any time the Fatigue Index exceeds 200, this is cause for concern. As you can see, Robles reached an FI of 224 on April 13th, which given how early it is in the season, is absurd. It's worth noting, however, that last year, Robles was the first pitcher to reach an FI of 200 or higher, having done so on April 20th, 2016, with an FI of 214 - Addison Reed followed suit on April 26th, with an FI of 205. The amazing thing, however, is that despite how quickly Reed and Robles reached the 200 mark last year (they were on pace for about 1,400+), the highest it ever went to was 279, which Reed did towards the end of the season. (279 was the highest FI attained by any Mets pitcher last year at any given time, as well.)

The hallmark of pitcher abuse, though, is the rate in which the FI increases over time; here, I depicted that with a 4-day differential (I know there's a better way to depict this, as I'm still working on it). As you can see, the 4-day FI differential for Robles between April 13th and April 9th is 158, which is exceedingly high. In fact, no relief pitcher last year had a 4-day differential higher than 149 (which Fernando Salas had as an Angel, on May 14th - see, it's not just TC).

I wanted to cover this topic more comprehensively and in-depth, in time for the return of Jeurys Familia; however, I haven't been feeling well the last few days (particularly, on Tuesday). Think of this as an introduction to tracking pitcher usage and spotting pitcher abuse; I'll dig deeper in Part 2, with more actual data to present.

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