推 hsiaoyoshye:Ellsbury can save 14-18 runs for redsox 03/02 09:55
推 DoMoe:快速翻譯：Theo口嫌體正直 03/03 00:43
http://www.fangraphs.com/blogs/index.php/theo-ellsbury-and-uzr
by Dave Cameron - March 1, 2010
Last week, Red Sox GM Theo Epstein did an in-depth interview with WEEI,
focusing mainly on the topic of the winter – defense, defensive
statistics, and how most of the stat-friendly teams have made moves to
improve themselves defensively in recent years. During the interview, he
made one specific comment that we feel is worth addressing, since it was
aimed our way. In response to a question about whether Jacoby Ellsbury
had defensive problems in center field last year, Theo said this:
I think that he is an above-average center fielder now, who is going to
be a great center fielder. I know there is a certain number we don't
use that is accessible to people online that had him as one of the worst
defensive center fielders in baseball last year. I don't think it's
worth anything. I don't think that number is legitimate. We do our own
stuff and it showed that he is above average.
Since we publish that "certain number" – more often referred to as
UZR – let me weigh in with a few thoughts.
UZR, with its -18.6 rating for Ellsbury in center field in 2009, isn't
exactly out on an island here. John Dewan's +/- metric had him at 9
runs below average. Sean Smith's Total Zone system had him at 10 runs
below average. Tom Tango stated that his With Or Without You system had
him between 14 and 18 runs below average. This isn't a case of UZR
delivering a strange result that other systems don't agree with. Pretty
much all of the publicly available defensive metrics show Ellsbury had
some issues last year.
Now, Theo might lump all of those metrics together as inferior to their
proprietary internal metrics, and indeed, they may be. However, we need
to keep two things in mind here: first, Epstein making positive public
comments about his own players is a classic case of a statement made in
self-interest, and second, the Red Sox moved Ellsbury to left field.
Theo's not going to come out and trash any of his own players, and
it's in the Red Sox best interest to fight any perception of Ellsbury
as a defensive liability. If they engage in trade negotiations with
another team, it would not be helpful if the league comes to a consensus
that Ellsbury really does have some defensive issues, considering that
is the biggest selling point for his particular skillset.
The Red Sox decision to move Ellsbury to left reinforces that idea. If
Theo had left it unchallenged, it would essentially amount to a tacit
acceptance of the rating, which would not be good for Jacoby’s trade
value. Even if the Red Sox internal metrics had not shown Ellsbury as
above average, it would still behoove Theo to publicly defend his player
against the perception that his defense in center field may be
questionable. Once the Red Sox decided to shift Ellsbury over, it became
necessary for Epstein to make a statement to this effect, whether he
believes it or not (and I'd bet that he does – this is not intended to
question his integrity).
Finally, this is a big point – Jacoby Ellsbury played 1,302 innings in
center field last year, basically one full season's worth. As has been
noted many times, one season's worth of any defensive metric is not a
very large sample size. Due to the amount of marginal plays that a
player is judged on over the course of a single season, a few bad breaks
here or there can make a pretty significant impact on a player's
overall rating. We have always suggested that you want more than one
year of data before you start making judgments about a player's true
worth defensively. No one should look at Ellsbury's 2009 UZR and state
definitively that he is a poor defensive center fielder.
In fact, UZR doesn't even support that assessment. In 2007 and 2008,
Ellsbury racked up a +14.4 UZR in 777 innings between left and right
field. That equates out to about 20 runs above average, if you
extrapolate out over a full season. UZR loved Ellsbury in the corners,
and historically, the defensive gap between a CF and a corner OF is
about 10 runs. Given how well UZR rated him as a corner outfielder
(again, in a very small sample), we can use that data as information
about how well he should be able to handle center field. An overall view
of Ellsbury through UZR, including all of the data from 2007 to 2009,
would have him as a barely below average CF, not anything close to a
disaster, and not that far from what Epstein is claiming.
There is a school of thought that these swings suggest an underlying
flaw with UZR, but I'd suggest that it may be evidence that the
perception of perfectly consistent defensive value is a myth. We know
that hitters and pitchers often see wild swings in their performance,
but no one thinks its proof that home runs are bunk when David Wright
gets out-homered by Ichiro Suzuki. Wright obviously has more power, but
over one season, he didn't show it. It is certainly reasonable to
believe that a player that Epstein believes to be "a good defensive
center fielder" could simply have a bad year.
In the end, there's no huge disagreement between FanGraphs and the Red
Sox on how to evaluate defense, even if they prefer their internal
metrics to UZR. We love the defense that Mike Cameron and Adrian Beltre
provide and, obviously, so do the decision makers in Boston.
Additionally, that Ellsbury was shifted to left field to make room for a
37-year-old suggests that the Red Sox may agree that he's not yet an
elite defender, even if they think he may become one. In this instance,
I think that actions may speak louder than words, and I don't think
that Theo sees Ellsbury all that differently than we do.
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