A Defensive Stats Primer
Defense! Defense! Defense! Can’t tell the difference between a Zone Rating, a Range Factor, or a Max Factor? Hit the link to get clued in.
Baseball is made up of two things scoring runs, and preventing runs from scoring.?
The pitcher is all about keeping runs from scoring and the Designated Hitter
is all about scoring runs.? Any manager using a weak hitter at DH is clearly
unfamiliar with the purpose of the role.? Every other player has two parts to
his game ? his hitting and his fielding.
Offense has been studied thoroughly.? There are
many ways to evaluate offense: batting average (BA), on-base average (OBA),
slugging average (SLG), Runs Created (RC), Extrapolated Runs (xRun), Linear
Weights (LC).? The last three offensive summations do a really good job of describing
how runs are scored on a team level, and that is subsequently extended to the
individual players.? All of these methods are readily available around the Web,
with xRun?s progenitor being BB Primer?s own Jim Furtado.? You can read all
about it in the glossary.? You can calculate the approximate value of every
player, and essentially determine the league?s offensive MVP.
Defense is a bit trickier to measure.? Is it the
pitcher getting the hitter to hit into easy plays, or is there a big difference
in defensive players?? A quick glance at each team?s opponents? batting average
will tell you there is a limited amount of contribution a single defensive player
can make.? The important question is how much better is a defensive player than
the available alternatives, and ultimately his peers.
The common defensive statistics, unlike offensive
statistics, stink.? First there is ?Number of Gold Gloves Won.?? What do Gold
Gloves say about a player?? As I read Dan Szymborski write the other day, ?he
got the most votes.?? There is no objectivity to Gold Gloves whatsoever.? The
voters usually vote for the player with a good reputation, regardless of actual
skill level.? This really came to light in 1999 when Rafael Palmiero won the
award after playing just 28 games at first base for Texas.? Sometimes a good
fielder wins the award, sometimes not.? So using ?Gold Gloves won? is essentially
useless for determining who is a good fielder and who is not.?
Next is fielding percentage (F%).? It?s nice to
have a good fielding percentage, but it does little to tell you about how good
a fielder is.? Two shortstops get 100 balls hit in their general direction.?
Shortstop A fields 85 of them and makes no errors.? The other 15 are out of
his range.? His fielding percentage is 1.000.? Shortstop B fields all 100.?
He makes 5 errors (fielding or throwing).? His fielding percentage is 0.950.
?The difference between the two is not that SS A is better; in fact, he?s worse,
but has a better percentage.? Pardon my blasphemy next: many of the ?great fielders?
were really just limited in range.? Larry Bowa was a fine shortstop and has
the highest fielding percentage for a career at short.? But Dave Concepcion
was much better.? He just could range further, turning grounders into outs that
Bowa was unable to reach.? Fielding percentage may be a good indicator of sure-handedness,
but it doesn?t do a good job at all for determining who the better fielder is.?
In the ?80s, Bill James came up with a statistic
called Range Factor (RF).? At first blush, this appears to be a good idea.?
It is calculated by dividing plays made by games played.? This provides the
number of outs a player made per game.? By comparing fielders to one another,
one could quickly see that Ozzie Smith was making 5.5 plays per game and Garry
Templeton was making 5.0 plays per game.? At 0.5 more plays a game for 160 games
meant 80 singles!? Wow!? And that?s how a legend is born.? Bill James is known
for giving rise to a new way to look at baseball: analytically, rather than
just nodding along to the clich?s.? RF is not a statistic to use if anything
else is available.? RF was modified to be calculated to plays per 9 innings.?
What RF misses is the critical aspect of chances.? The reason Ozzie made 0.5
more plays per game is because he had more balls hit to him.? Ozzie had a lot
more groundballs hit to him. That?s a big help.? The aspects of a fielder?s
pitching staff influence this statistic more than most. Range Factor, because
of its source and relative ?newness?, finds popularity in people just delving
into the atypical statistics of baseball.? To me, that?s bad; very, very bad.?
RF may have value over a career, but in today?s game, I think it is the worst.
So what do we do for a defensive statistic that
doesn?t stink?? We start scoring baseball games for the fielders in addition
to the hitters.? How?? We write down every ball that?s put into play, and where
it was hit on the field.? There is a company that does this:? STATS, Inc.
STATS, Inc. is a company that hires people to watch
baseball games.? These people write down every pitch.? They write down every
play.? This is where we get information about how hitters perform with runners
on second and two outs.? This is done to record what location every ball put
in play was hit.? This is where we get information about how many times a pitcher
throws to first base during each game.? Each ballpark has a grid with labeled
?zones?.? When a ball is put in play, the STATS scorer records the pre-labeled
area of the field that the ball was hit to; how far the ball traveled before
being picked up; whether it was a fly ball, a line drive or a ground ball, and
an estimate of how hard the ball was hit.? The scorers do not make any judgment
with respect to whether or not a fielder should have made the play.? This is
critical because it removes the primary source of subjectivity in a player?s
evaluation. ?STATS usually has several people watching every game.? Multiple
game scores can be cross-checked to insure accurate ?zone? assignments for each
ball in play.? It?s really a strong network of data collection, but it is not
So you say, ?Dial, what does that have to do with
the price of peas in Peoria??? And I answer: it?s how we can see how well a
player does compared to his peers defensively.? The data accumulated by STATS
is reported (at STATS on AOL, CNNSI.com, ESPN.com) as a zone rating.? Every
player has one, and it is close to the fraction of balls a player converts into
outs divided by balls hit into a player?s zone.? A player gets a bonus for getting
to balls outside his zone.? For a good visual, consider the standard position
for each player:? where the shortstop stands, where the second baseman and centerfielder
stand.? For infielders, imagine a 20-foot circle around each player.? That?s
the area each player is expected to cover.? All shortstops are responsible for
the same zones.? Since they all are assigned the same zones, and they all stand
within a few feet of each other on the field, the percentage of balls they turn
into outs should be a mostly accurate description of how well they field.? Zone
Rating (ZR) is not a perfect measurement, and should only be described
as good.? It will undervalue defense because it doesn?t consider the ability
to get to pop-ups and turn double plays.? If you need to make a judgement on
how good a fielder is, try to use ZR at a minimum.
Unfortunately, there is no ZR data older than about
1985.? That means the Gold Gloves, the fielding percentages and range factors
for all the older players will have to suffice.? There are a few systems attempting
to measure fielding using play-by-play data, and they may improve on what we
presently have, but one must always recognize the shortcomings of these systems
and of the statistics gathered today.
Posted: March 06, 2001 at 05:00 AM | 3 comment(s)
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