On May 13, 2013, Dustin
Ackley got sent down from the Seattle Mariners to its AAA affiliate in Tacoma
for some additional work after starting the season with a horrendous
"slash line" of .205/.266/.250 (BA/OBP/SLG).
Yeah, a .250 SLG.
For fun, let's look at
some other ways you can achieve a .250 SLG:
1.
Go 1-16 with a HR and 15
groundouts
2.
Go 16-64 with 16 singles
3.
Show up to the field late, go 1-4 with a single, go to McDonald's
after the game
Dustin Ackley reeeeally
just kinda sucked at the start of last season. Seems like a cool guy, but
man, those numbers aren't gonna keep you around long.
Anyhow, point of this
story is: Tacoma is where he apparently got good, again, in
the eyes of some. He got promoted after a month and then had a tremendous
second half of the year in the major leagues.
As Larry Stone reported, Ackley snagged a copy of
H. A. Dorfman's The Mental Side of Baseball while he was in
Tacoma. This is a well-known book... about... the mental side of baseball,
essentially. And Ackley says it changed him. It taught him he
mostly needed to improve his mental state, above anything else.
Ignore the swing for a
while. It is fine. Just get your mind right.
This change happened
about 12 months ago from today. What I want to do is figure out whether
he is actually better now, than he was before. We'll have a look in a
moment.
First, please remember,
as always: correlation does not imply causation. Even if we see improved
performance since he read this book, that isn't proof that the book caused the
improvement.
But I would argue
strongly that there probably is some degree of causality in this case. I
definitely believe there is a general causality between a player's mental state
and his performance. This is where I take off my analyst hat and just
rely on experience and gut feel.
Anyways...
The Data
Of the above metrics,
wRC+ is the most highly-correlated to team wins, so let's just focus on it for
a second. +100 wRC is a good way of defining a league-average hitter. At +97 wRC, Dustin Ackley has basically been a league-average hitter, for
the past 12 months. That's the first thing to note.
More to the point here,
since the commencement of the mental revolution, has Ackley performed better? Well, he's definitely not worse. He's a little bit
better. He was a 16% below average hitter (84 wRC+), and since that time
he is 3% below average (97 wRC+).
Do we have a large
enough sample size to believe his new true talent level has changed? Probably not. We have 464 PAs - less than one season's worth of batting
data.
Over the course of just
one season, strange things happen. Bill Mueller won the AL batting title
in 2003.
12 months from now, if
Ackley remains a healthy MLB starter, we will have 2 full season's worth of
post-revolution Ackley data. At that point, his sustained improvement
would be twice as meaningful. We would probably be about twice as confident his true
talent level has changed.
But even then, a year
from now, if Ackley remains league-average ish, or better... we still won't
definitely be able to say that H. A. Dorfman's* book changed him. Nope. Until we have some sort of scientific method available for this type of
analysis, I'm afraid we cannot prove that, beyond a reasonable
doubt.
But it doesn't mean it's
not the truth, either.
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