Tuesday, March 01, 2011

Comments on Bill James Gold Mine 2010, pt. 2

2. Defensive Win Shares and Loss Shares

James has revamped Win Shares over the last couple of years to include Loss Shares. I think this is a very good thing, although I look forward to when (if?) the entire methodology is published. Without the full explanation, it's dangerous to comment about isolated details, but James' essay on "Explaining Defensive Win Shares to a Dead Sportswriter" is tough to ignore. My Twitter-friendly take on it: He's going to have trouble explaining it to a lot of people, not just dead sportswriters.

Again, it's impossible to evaluate the method while knowing so little about it, but James makes this extraordinary statement:

Making outs increases the team's responsibility to play defense. When you make more outs, that increases the team's responsibility to play defense. Therefore, if two players are the same in the field but of them makes more outs, the one who makes fewer outs has to come out ahead when you compare the player's defense contribution to his defensive responsibility.

Lest you think that was just a slip, he doubles down:

While we are in the habit of thinking of offense and defense in baseball as un-connected, they are in fact not un-connected. There is a very important connect between them, which is the rule that for every out you make on offense, you must record an out on defense.

Bill James is obviously a very intelligent man, and you a very intelligent reader, so I am hesitant to respond to this--the response should write itself. Limiting myself to a paragraph or less, I suppose it is technically true that each out on offense is matched by a defensive out, barring walkoffs and rainouts and the like. But there is no causation between the two. The rules of the game require three outs per inning and nine innings per team. Each team makes 27 outs regardless of the rate at which they use them (think OBA) or any other factor.

An individual who makes outs at a higher rate than some comparison player does not increase the number of outs that his defense must record. The defense must record 27 outs regardless of what an individual does at bat. What does happen is that by consuming excess outs, the individual batter leaves less outs to be consumed by the other eight members of his lineup, and fails to generate additional plate appearances for them.

James later seems to suggest that the revamped DWS-LS system assigns the same responsibility to field to each position, regardless of where it stands on the defensive spectrum. He then states his objection to offensive-based positional adjustments, and so it seems as if the stuff about making outs might be a backdoor way of applying positional adjustments. It's unclear, though, and still doesn't follow logically.

James’ discussion of positional adjustments also seems to gloss over the use of defense-based positional adjustments or the fact that most of us who still use offensive positional adjustments do so because we believe they provide a ballpark estimate of the defensive differences between the positions. When I use an offensive positional adjustment, I'm not saying that I think a shortstop with a 5 RG is a better hitter than a first baseman with a 5 RG. What I am saying is that the difference between aggregate offensive performance between shortstops and first baseman (when considered carefully and over a long period of time) approximates the inherent difference in defensive value.

You are certainly free to reject that argument (and many sabermetricians that I respect very much do just that), but please recognize that the sabermetrician using an OPADJ is likely not making the claim that a player's offensive contribution is altered by his fielding position.

More important than my own positional adjustment folly is an apparent failure by James to recognize that the positional adjustments that are now used most prominently in the community (generally Tango's, which have made their mark on the PADJs used in WAR figures from both Chone and Fangraphs) are based on estimates of the defensive difference between positions, sometimes informed by offensive averages. Furthermore, the sources do not lump the positional adjustment into the offensive ranking--they break everything (offense, fielding, baserunning, position, etc.) into smaller components, which are then summed to produce RAA, WAR, or some other total value metric.

Again, it is possible that I have misunderstood James' point, or that he has done a poor job of expressing himself, and that DWS is completely logical. However, I think it is going to take a much more thorough explanation of the system to give people that read the Gold Mine piece a lot of confidence in his methodology.

3. Strikeout rate

One of the most thought-provoking essays is "Whiff 7", which discusses the phenomenon of strikeout rates continuing to reach all-time highs. James argues that there is no end to this in sight under current conditions, as teams have an incentive to find power pitchers but no disincentive to find batters that avoid striking out. James argues that the standard deviation of power (he doesn't use that terminology) has decreased over time, and so league homer rates have gone up while the top individual performers hit about as many homers as they did in previous eras.

James then offers some suggestions of rule changes that would slow or reverse the trend. It's an interesting piece, and it didn't prod me to respond to it directly, but rather to make a tangential and mostly unrelated point about how we measure strikeout rates--a wholly unoriginal and stale one at that.

I have for a long time advocated using K/PA rather than K/IP as the measure of pitcher strikeout proficiency (I’m not claiming this is unique, as others have carried that banner with much more vigor and coherent arguments than I have offered). Through no effort of mine, the use of K/PA has increased in the sabermetric community, with sites like The Hardball Times and Fangraphs prominently utilizing K/PA.

As an example of how the different denominators can change perception, consider the point that most long-term successful pitchers have at least average strikeout rates. This is a point that the average fan still mystifyingly misses a great deal of the time. Take Greg Maddux for example. Maddux is apparently seen by some as a non-strikeout pitcher. Here is a table with his K/9 versus the league average, with KAA being strikeouts above average per inning:



For his career, Maddux struck out 6.1 per nine, while the league average was 6.4. He struck out 206 less batters than an average pitcher would have in the same number of innings. Without seeing the same figure for a lot of pitchers, it's hard to contextualize that, admittedly.

Suppose that instead you look at Maddux through K/PA:



Now Maddux' strikeout rate is essentially average--he struck out 17% of opposing batters, the same as the league average. Maddux' career rate is lower (it's actually 16.5% to 16.6%), but just barely so, and by this metric he only recorded 22 less strikeouts than average.

In Maddux' peak years (I think 1992-98 stand out), he was above-average even by K/9--+90 KAA, while he was an even more robust +196 when K/PA is the standard.

This is not intended to recast Maddux as a strikeout fiend--certainly he was not, even at his best. Still, Maddux' strikeout rate is more impressive when viewed in light of the number of opposing batters he actually faced rather than in terms of innings pitched, which really is just a measure of the percentage of outs a pitcher gets via the K rather (this is obscured by displaying strikeouts per 9 innings rather than strikeouts per 27 outs).

In addition to K/9, there are several other per-inning pitching ratios in common usage--H/9, W/9, HR/9, WHIP. What all of those have in common is that they are ratios of bad things (offensive successes) to good things (outs recorded). K/9 is a ratio of really good things (outs recorded by strikeout) to another set of plain old good things that includes the really good things (total outs recorded). As such, it's best viewed as a measure of a pitcher's reliance on strikeouts.

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