Quiet Nats Blog
One of the reasons Nats Blog went dark yesterday is that DM's comment on my post about free agent pitchers got both me and DM thinking about a way to put a pitcher's strikeout, walk and home runs allowed totals into one simple statistic (which I have have been calling OneStat).
Both DM and I have been noodling the idea and we've come up with a rough version of it, which we need to back-test against data. But it looks something like this:
K/9 * K/BB
---------------
1 + HR/9
The resulting number shows that (no shocker here) that Ben Sheets and Randy Johnson were the best starters in the National League in 2004. But it also reveals some non-obvious comparisons. Odalis Perez had a 3.25 ERA and an ERA+ of 127 in 2004. At the same time, Kris Benson had a 4.31 ERA and a 97 ERA+.
But the value of Perez vs. Benson is not so easy. Here are some key stats from both of them last year:
| Name | IP | HR | BB | K | ERA | ERA+ | OneStat |
|---|---|---|---|---|---|---|---|
| Perez | 196 1/3 | 26 | 44 | 128 | 3.25 | 127 | 7.79 |
| Benson | 200 1/3 | 15 | 61 | 134 | 4.31 | 97 | 7.9 |
ERA and ERA+ wise, it looks like Perez was a much better pitcher. But dive into the peripherals, and you'll see that Perez gave up 11 more homers (pitching at Dodger Stadium, nonetheless), and struck out 6 fewer folks. Benson had 17 more walks, but that simply doesn't explain the 1 run difference in ERA and 30 point difference in ERA+ (one would think the 11 fewer home runs would more than compensate for the extra 17 walks).
Anyway, DM and I continue to noodle this, but it is something worth further thought, and we would appreciate any input you have.
posted by SuperNoVa @ 9:19 AM
5 comments
5 Comments:
John,
Can you get me a link to a site that has DIPS? I can't seem to find dERA or any other DIPS at baseballprospectus.com. I've got a subscription, so if you post a deep link, I can get to it.
OK, John, I just found dERA for Benson and Perez:
Benson: 4.45 PIT / 4.67 NYM
Perez: 3.70
Based on their peripherals, wouldn't you expect their to be little or no difference in their dERA's? What is wrong with the picture here?
Doesn't the OneStat show that they are much closer in terms of performance independent of defense?
John, at bottom what we are doing is the same as DIPS, and based on the same theory. What I wanted was a simple stat that looked at only SO, BB and HR, that would not be hard to compute on the fly when looking at a pitcher's stats. As I understand McCracken's DIPS and even dERA, they use the principles to come up with a set of pitcher stats adjusted to be defense independent. I just want something easier to calculate at hand.
Ever since I read on DIPS, I've made a point to focus only a pitchers SO, BB and HR when reviewing a guy, just to get a sense of how useful DIPS is. If it really is the case that most of pitcher's effectiveness can be isolated in these stats, then that is all we should need to look at to get a sense of what kind o pitcher they are.
I ran the OneStat for the 2004 Phils (my home team and one I followed pretty closely all year thanks to DirecTV and MLB.tv). The rank it gave was pretty consistent with how I viewed the value of each pitcher on that roster. Sure, that's anecdotal, but all I want is something in the ballpark.
In English, OneStat is measuring absolute strikeout rate (K/9) against relative strikeout to walk rate (K/BB) against absolute home run rate (HR/9). Since there is a possibilty of zero home runs, we add 1 to HR/9 to ameliorate the Div/0 problem. We also add 1 because very low home run rates (.5 HR/9 or less) have a distortive effective because dividing by a number less than 1 has a multiplicative effect.
The purpose is to measure all three stats at once. It is not to define the quality of a pitcher (although better pitchers would have better OneStats)...it's just to combine the stats. That's all.
Jeez, John, now you're just getting insulting. You call it a crap stat without any testing of the data at all. It very well may be a crap stat! I agree! It may be the worst thing ever conceived. But I've played around with and my initial, non-scientific reaction is that, hey, it seems to fit reality OK. We are at the point of the hypothesis stage. Our hypothesis is that OneStat (we really need a new name) explains reality well and is a fair combination of three (or 4 if we include HBP) defense-independent statistics. The burden is on US to prove the hypothesis, which we haven't done, I agree. This idea is THREE DAYS OLD. Did Bill James put his Win Shares out to the public 3 days after he drew up his first formula for Win Shares?
Have you performed an analysis to check whether OneStat, for example is a better predictor of the next season's ERA than, for example, dERA? Nope, neither have I. But I don't think it should be dismissed (nor should it be embraced) without further analysis.
Moreover, are you not troubled by the 0.70 difference in dERA between Benson and Odalis Perez? I certainly am. It doesn't explain reality very well in that particular pairing. Of course, there are thousands of possible pairings from which assessments of reality could be drawn - the Perez/Benson problem is not the only one out there. There may be a reasonable explanation for dERA's superficial failing. And it's true, I don't have a deep understanding of dERA; there is no real explanation/equation for dERA at BP.
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