※ 引述《Westmoreland (Westy)》之銘言：
: * 單季最多局數出現在 2010 之前
: Tom Verducci 使用這種觀察方法檢視過去六年
: 危險名單總共 55 人，其中 46 人 (換句話說是 84%)
: 在下一球季受傷或是 ERA 腫脹
: http://sportsillustrated.cnn.com/2012/writers/tom_verducci/
: 01/18/year.after.effect/index.html
: http://tinyurl.com/7pe8ooe
: 嚴格來說這沒甚麼理論基礎，當參考就好
The Verducci Effect Is Overworked And Broken Down
http://tinyurl.com/7zpnazf
Sports Illustrated's Tom Verducci came out with his annual "Year After
Effect" column yesterday, based on his hypothesis that that young pitchers
tend to break down the season after an increased workload. Specifically, a
pitcher 25 and under is supposed to be at risk if he pitched at least 30 more
innings than his previous career high.
Dubbed the "Verducci Effect" by Will Carroll at Baseball Prospectus, it's one
of the most prominent early examples of a happy marriage between analytics
and old journalism. Sabermetricians were some of the loudest critics of the
overuse that may have contributed to the early decline of Mark Prior, Ben
Sheets, and other pitchers who debuted in the early aughts.
But the Verducci Effect probably doesn't exist. Its continued popularity has
little to do with the power of numbers to support rational observation and
everything to do with their power to baselessly reinforce existing beliefs.
The article is an example of three pervasive mistakes that the general public
makes about statistics:
‧ Regression to the mean: When an outcome is far above or below expectation,
the subsequent results tend to be closer to the average. How does a young
pitcher make Verducci's list? By having been healthy and successful enough to
earn a greater workload. So by chance alone, you'd expect some members of
that group to pitch worse, and you'd certainly expect to see some of them get
hurt. Derek Holland's good health allowed him to pitch 71 more innings than
he ever had before. If he gets sidelined in 2012, it will have more to do
with the random nature of injuries than with Rangers mismanagement.
‧ Confirmation bias: People tend to rely on anecdotal examples that confirm
what they already think. There's little attention paid to the pitchers who
repeat their healthy seasons the year after; instead, fans fixate on the ones
that get hurt. Mets fans might look at Jon Niese's 2009 injury and point to
Verducci's warning label. They'd be ignoring the fact that no other pitcher
that Verducci identified in '09 spent a single day on the disabled list.
‧ Correlation does not equal causation: Verducci is correct that some
pitchers who pitch 30 innings more than their career highs tend to get hurt.
However, that doesn't mean that his rationale for why that happens is valid.
After I read his article, I went to the bathroom and peed. That doesn't mean
I peed as a result of reading.
Every study I could find on the Verducci Effect suggests that it at best
doesn't exist and at worst is backwards. David Gassko's 2006 study focused on
the possibility of a decline in performance, and found an increase:
OK, so what happens if we limit ourselves to pitchers who threw at least
100 innings in year two? Actually, a funny thing. The pitchers who best their
career high by at least 30 innings go on to throw 90% more innings in year
three than they do in year one, and those who didn't only throw 78% as many
innings. What's more, while the [year-after effect] candidates have an ERA 9%
lower in year three than it was in year one, the guys who were accustomed to
the big workload do not improve their performance at all.
Jeremy Greenhouse's 2010 follow-up focused on injuries and also found
nothing. JC Bradbury came up empty. Brian Burke used a card game to show how
randomness, not overuse, is the likely culprit. Tom Tango expressed his
concerns (there's elaboration in the comments.) Scoresheetwiz found nothing
too.
Verducci's find is the Sports Illustrated Cover Jinx in a new dress. Athletes
grace the SI cover because they've done something extraordinary; it's
reasonable to expect that they would return to being average by the time the
issue is in your recycling bin. Yet the idea of the jinx endures, because
people notice when an athlete sucks after being on the cover and ignore the
players who continue to do well.
It's time for Verducci to retire the Verducci Effect until someone comes up
with evidence that an increase in workload has anything to do with a decrease
in productivity in the following year. It's not even a rule of thumb or a
kludge at this point, as the pitchers he picked out are probably more likely
to succeed in 2012, not less.
I don't blame Verducci much for continuing to write the articles. He deserves
a lot of credit for coming up with an interesting hypothesis—it's not his
job to use advanced analytics to prove or disprove it. A lot of the fault
lies with Baseball Prospectus's and Carroll's stubbornness on this particular
point. He now insists that it's just a general warning about overuse and that
"people who quantify it strictly are missing the point." But given the rule's
origins as a hard-and-fast limit, he's just asking for writers without
statistical backgrounds to misinterpret it. Here's the BP glossary entry for
"Verducci Effect:"
Named for Tom Verducci of Sports Illustrated, this is a negative forward
indicator for pitcher workload. Verducci, who called this the 'Year After
Effect,' found that pitchers under the age of 25 who have 30-inning increases
year over year tend to underperform. Will Carroll independently found that
pitchers who break the "Rule of 30" tend to get injured. Carroll renamed this
'rule' the Verducci Effect in honor of the man who initially found the
evidence.
It's time for a new definition.