07/11/2006 12:33 PM ET
Security Service Field: Context Matters
"For me context is the key - from that comes the understanding of everything".
- painter Kenneth Noland
In June, Mike Claus wrote two fine articles under the
banner "Understanding Stats" in which he delved into first hitting and then pitching statistics to explain the usefulness of metrics such as
SLUG, OPS, WHIP, and GO/AO ratio. And while these metrics are indeed excellent
for giving you a quick overview of just how productive a hitter has been or how
effective a pitcher has performed, in their raw form they leave out a critical
aspect that should interest Sky Sox fans as much as any other fans of
That aspect is the physical context in which the
The Sky Sox play their home games at Security Service
field which was built in 1988 (then called Sky Sox Stadium), recently remodeled
and is now a first class venue for minor league baseball which this author
visits as often as possible. Security Service Field also has the distinction of
course of being at the highest elevation (6,531 feet) of any North American
professional baseball park. At that elevation, as with Coors Field in Denver but
to a smaller degree since Coors is over 1,000 feet lower, the game literally
takes on a different air.
At this higher elevation there are three primary affects.
First and most obviously, a baseball travels farther when hit because of the
thin air. Physicist Robert K. Adair who was once appointed "Physicist to
the National League" estimated that a 400 foot fly ball at sea level would
go 40 feet farther in Denver which of course means it would fly even farther in
Colorado Springs. Second, storing baseballs in the low humidity environment has
causes them both to shrink and lose weight, which conspire to make them fly
even farther. Because of this, the Rockies have gone to storing baseballs in a
locker dubbed "the humidor" where the humidity
and temperature are controlled so as not to allow the balls to shrink
and lose weight. And finally, on top of the first two effects, the thinner air
means that pitchers have more difficulty getting their breaking ball to bite
although their fastballs appear a bit livelier. As a result, it makes the job
of Sky Sox pitching coach Chuck Kniffin especially trying.
season Rockies directory of player development Marc Gustafson agreed
that it takes a special pitching coach to help pitchers succeed in what is for
the most part, an adverse environment.
"It's a valid
point that the pitching coach for the Sky Sox might be the most important and
demanding job in minor- league baseball. Most definitely pitching there
prepares a pitcher for Coors Field. You have to have the mentality of a doctor.
Pitchers have to learn to be tough- minded and to handle adversity."
So how does this relate to the statistics of
Sky Sox players?
Simply put, since the environment is indeed a
bit different at Security Service Field the performance of the players, and hence their statistics, will tend to reflect that difference.
Luckily, people who analyze baseball
statistics have run across this phenomenon many times in the past. It turns out
that it isn't only elevation that "distorts" a player's statistics.
For example, it has long been understood and it seems intuitive that the Green
Monster at Fenway Park, the short porch in right field and "death valley" in left-center at Yankee Stadium, and even the oval shaped Polo
Grounds where the New York Giants played for many years have an effect on the
number of doubles and homeruns hit in those parks which in turn effects
scoring. That means that when you take a player and move him from one park to
another, his skills might be the same from year to year but the park (the
context) in which he plays will make his statistics appear different.
To correct for the context performance
analysts created what are known as park factors. Basically,
these are multipliers that take into account the mix of home and road parks a
player performs in and can be used to adjust statistics for comparison. You can
think of them as numbers that encapsulate the total effect of playing home
games at a particular park which includes field conditions, weather, park
configuration, and yes, even altitude. A park factor of 1.000 would be a
perfectly neutral park that doesn't bias statistics either way while a park
factor of greater than one indicates a hitter's park while a factor less than
one indicates a pitcher's park. More granular park factors that take into
account only homeruns or only doubles or triples can and are also calculated
but we'll just stick to the total park factor here.
So if player a has an OPS of .850 but plays
his home games in a park like Zephyr Field in New Orleans with a park factor of
.907 (relative to the Pacific Coast League), one could adjust his OPS by
dividing it by the park factor to give an adjusted OPS of .937. On the other
hand if player B recorded an OPS of 1.027 but played for the Tucson Sidewinders
at Tucson Electric Park (park factor 1.096), his adjusted OPS would also be
.937. So while on the surface player A appears inferior to player B, by
accounting for the context in which they play we can more correctly view player
A's performance as on par with player B. The same can be done for a pitcher's
Earned Run Average (ERA).
There are several ways in which park factors
are calculated. At Baseball Prospectus we calculate park factors for every
major and minor league team and publish them in our yearly annual. The method we use is to calculate a
ratio of runs scored at each team's home park to runs scored in games on the
road and then apply a weighted average over a number of seasons to help ensure
that factors such as particularly strange weather one summer or a particular
mix of players don't skew the numbers terribly.
As you can imagine, for the Sky Sox at
Security Service Field the park factor is greater than one and in 2005 was
1.033, meaning that offensive output for Sky Sox players over the course of a
season is inflated just over 3%. But even with the high elevation the Sky Sox
park factor was only fifth in the PCL in 2005.
|Salt Lake City||1.081|
While on the surface this may seem a little
strange, keep in mind that park factors are computed relative to the league and
so it just happens that the PCL contains other cities at high elevation
(Albuquerque 5,314 feet, Tucson 2,389 feet, Salt Lake City 4,330 feet, Las
Vegas 2,178 feet,) and low humidity that offset some of the elevation at
Security Service Field. In addition, park dimensions, field conditions, and
configuration also play a large role in determining the park factor. Overall
because of these parks the PCL is often viewed as a "hitter's league"
relative to the other AAA league, the International League.
It turns out that in baseball, as with most
things in life, context matters. And certainly context matters at Security
Service Field as much as anywhere else.
This story was not subject to the approval of the National Association of Professional Baseball Leagues or its clubs.