Monday, February 14, 2005

The ERA of Innocence

Noah Lowry=William Van Landingham

-Icaros in comments today at Dodger Thoughts

I don’t mean to pick on Icaros, a valued member of the Dodger blog community. However, I think it’s significant that someone like Icaros – who I know puts a lot of thought into what he writes when he leaves blog comments – would write something like that.

Lowry and VanLandingham do have several things in common. They both pitched in college and they both debuted for the Giants at age 23. VanLandingham pitched 84 innings with a 3.54 ERA in his rookie season while Lowry pitched 92 with a 3.82 ERA.

However, Lowry is left-handed and VanLandingham was right-handed. VanLandingham had a 6.0 K/9 and 4.6 BB/9 while Lowry had a much better 7.0 K/9 and 2.7 BB/9 in his debut. VanLandingham made up the difference by only allowing 4 home runs in his 84 innings, an anomalously low number even if he was, as I seem to recall, a heavy groundball pitcher. Even so, VanLandingham’s ERA benefited much more from defense and fortuity than did Lowry’s.

On top of that, the way Icaros evoked Van Landingham seemed to suggest that Lowry’s success was unsustainable. That’s an odd comparison since Van Landingham had his best season in his second year. Maybe Icaros meant to compare VanLandingham’s second season to Lowry’s first season. His K, HR and BB rate in his second season actually closely resemble Lowry’s 2004 performance. However, the raw numbers are clearly misleading; the run scoring environment Van Landingham played in was much more favorable to pitchers, and relative to league average VanLandingham’s performance didn’t match Lowry’s. On top of that, comparing VanLandingham’s sophomore effort at age 24 to Lowry’s debut at age 23 isn’t exactly apples to apples.

So the two are, through the very early part of their major league career, both above average pitchers pitching three years after being drafted out of college. There are hundreds of pitchers that meet that criteria, and there’s not much to suggest that within that population these two are very similar. In fact, their different peripherals indicate that they’re pretty different pitchers.

So why compare them? Because they’re Giants! Plain and simple. Even though what team two pitchers play for ten years apart has less predictive value than their breakfast cereal, it’s easy to compare the two. We get suckered into a comparison because of our emotions toward the players. I remember the last time the Giants had some hot stud young college pitcher – what a disaster that was! If Lowry flames out, we’ll point to the VanWarningsigns and congratulate our collective memory. If he succeeds, we’ll probably forget that we once made the comparison.

This speaks to what I consider to be perhaps Bill James’ greatest insight. Baseball is full of numbers, he argued, but the typical application of numbers in baseball was based not on the contextual meaning of those numbers but on the emotional and associational impact of the numbers. .304 average? Sign me up! 31 home runs? Wow, a big bopper! James argued that his goal was to strip away that veneer and determine which numbers were important and why.

Treating two pitchers as similar because they played for the same franchise is clearly folly, and I’ll bet that Icaros realized that soon after his initial posting when other Dodger Thoughts commentators described differences between VanLandingham and Lowry.

But still, they seem so alike with those mid-3 ERA’s and IP totals. The thing is, ERA’s and IP are firmly entrenched in our way of thinking about pitchers despite being of limited utility. While most readers of this site are probably quick to mock anybody who trots out Run and RBI totals, ERA and IP aren’t too different from those stats.

In terms of predictive value, the number of innings a pitcher throws in one season doesn’t heavily influence the number he’ll throw in future seasons. There will be correlation, of course, because pitchers are used in fashions that reflect their skill set and because some pitchers have recurring injury issues. However, those are reflected in other statistics as well, and IP doesn’t tell you anything substantial about a player’s true talent level that couldn’t be unearthed with other metrics.

Similarly, ERA doesn’t have great predictive value. A player’s ERA’s will often end up being similar in many years, but it’s the components of ERA that matter in determining how effective a pitcher is. To project pitching performance, it’s necessary to look at how often a pitcher strikes batters out, walks batters, and so forth; it’s not necessary to look at the player’s ERA. The difference between a player’s ERA and what their component figures would predict can be useful, but not because of anything inherent in ERA; ERA is just a way of checking how the other parts of the system add up so that we can see how a pitcher deviates from the standard model in terms of concentration of baserunners and runs and so forth. Those are things which are at the margins of what we look for in a pitcher anyway, though, so ERA’s value in such an endeavor is limited. Moreover, the actual data on how a pitcher’s baserunners and runs are concentrated is superior to extrapolations from ERA, so ERA is at best an imperfect intermediary.

In addition, ERA is useless without reference to the scoring environment in which an ERA is recorded. A 3.00 ERA in a 6 runs per game environment is very different from a 3.20 ERA in a 4.5 runs per game environment, but ERA itself doesn’t elucidate the difference.

While IP and ERA don’t offer much utility in deciphering a pitcher’s true talent level and predicting future performance they do, on face, represent a decent measure of actual observed value. The number of innings a pitcher eats is significant and the average of runs allowed is useful. However, ERA is a poor measure of value; run average is much better, because pitchers have a substantial impact on the amount of errors committed behind them and since runners scoring after reaching on error still have to be moved over. Run average is the useful measure of value, and while RA should always be adjusted for defense in some manner to determine a pitcher’s actual value, ERA makes an adjustment for defense which is entirely ad hoc and doesn’t tell us anything about the pitcher’s value relative to other pitchers.

IP is a pretty good measure of value, although the number of outs the pitcher is responsible for is ultimately what we are looking for and IP takes some short cuts that detract from our ultimately attaining that knowledge. But in another sense, IP doesn’t give a very good sense of value since it treats every inning pitched as the same. While the majority of innings happen in contexts that are close enough to make the distinction meaningless, innings pitched at different times have very different values. Michael Wolverton’s Support-Neutral pitching stats are a way to acknowledge this, and the work of Tangotiger and others on leverage index and win probability added does the same thing. Even then, the overall value of a pitcher to the team depends on how good and how rested the rest of the pitching staff is. Thus, innings pitched, while meaningful for basic calculations of value when more detailed data is not available, is not the best way to assign value.

I don’t mean to say that we should discard IP and ERA, though I wouldn’t mind too much if we did. It’s just that they both represent small parts of the story but measure things that are close enough to what we want to know that we settle for them. That act of settling is, in most cases, not necessary, and it always brings with it a strong risk of distorting our perception.

The point is, the numbers that we look at in attempting to compare players should be tested on two fronts. The first is the data's ability to determine the player's true talent level and thus future performance. The second is the data's ability to determine the player's actual value over a period of time. ERA and Innings Pitched do neither very well, and the franchise a player is employed by probably doesn't do either one at all.


Comments:
My Lowry=VanLandingham proclamation was not a statistically arrived at conclusion, just a hopeful one.

Reason sometimes flies out the window when it comes to hating the Giants.

However, I recall reading more than once that Lowry's numbers last year were far above his minor-league projections, leaving open the strong possibility for regression.

I don't have his minor-league stats, nor do I know enough about each particular league to determine their relative value.

So, Tom, did he pitch over his head last season, or is Noah Lowry really the next great Giant hurler?
 
Lowry's performance in the big leagues was his best at any level, but not by a big margin. His ascent was somewhat more rapid than is typical, but he didn't outperform his major league projection by too much. His ERA's in Norwich and Fresno look high, but they're inflated relative to his actual performance. Lowry's TTL is probably about 5-10% above league average at this point, and in his peak that could reasonably be 25-30% or so.
 
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