I've been working on a pitching evaluation tool and thought I'd post
it here to get some feedback.
I call it "Defensive Independent Pitching" and what it does is
evaluate a pitcher base strictly on the statistics his defense has no
ability to affect (it uses Home Runs and I guess technically a CF can
stop a HR every now and then but I think that's more or less
insignificant). The stats which play a main role in the calculations
are BFP, HR, BB, SO, HP, IBB. These stats are all "rated" by number of
BFP except for BFP (of course) and IBB (which are rated by total BB).
The process works as follows:
1. The rates of each of the above stats are adjusted for the pitchers
home park using a set of park factors.
2. The rates of each of the above stats are adjusted for the league in
which the pitchers pitch (The AL is the benchmark league so NL
Pitchers are adjusted to AL standards and AL pitchers are not affected
by this step).
3. The above stats are then "reassembled" to once again resemble
counting stats. i.e., the BFP stays the same the new K/BFP is
multiplied to BFP to get new K. Then BB/(BFP-K) is multiplied by the
new (BFP-K) to get the new BB, etc. on down the line. We now have the
above stats calculated for our Defense Independent Pitching Stats.
4. League Average (In this case the AL) rates are then assigned to the
remaining basic pitching stats, H, 2B, 3B, OUTS etc., based on all
BFP's which are not the above defense independent stats. We now have
another set of counting stats.
5. The counting stats are then used to come up with an earned run
total. I used Jim Furtado's Extrapolated Runs and then multiplied a
factor to make them on line with actual Earned Run Totals.
6. At this point we have a line of pitching stats just like a
traditional line of pitching stats. However the new line has now
removed virtually any effect the defense could POSSIBLY have on the
pitchers stats. This point can't be stressed enough. I'm not drawing
the assumption that pitchers can't have any effect on singles,
doubles, triples etc., I'm simply saying that the defense CAN affect
these things and we're often uncertain to what extent these effects
are. A study of those stats I did using Sean Lahman's database showed
that non home run hits from season to season correlated very poorly
for pitchers from year to year (about .2-.25). They correlated worse
than HR (.45-.5) and much much worse than BB and K (.65-.8). I think
this approach is radical enough to provide insight that other methods
don't as most other methods give the pitcher complete credit for his
1B, 2B and 3B totals.
7. The new earned run totals can be used to calculate an ERA but I
also used it to create an earned runs below replacement value which
for now will serve as the overall "rating" for each of the pitchers.
The League Average ERA in the AL last year was a very high 4.86. That
will also serve as "average" for these stats. I used an ERA of 5.98 as
a replacement ERA (after some fiddling. It was originally higher, but
at that point the highest relief pitcher, Keith Foulke was about 53rd
behind some guys that were barely average starters. With the new
replacement level Foulke climbed up into the top 30).
For the following post there will only be three categories:
ERA=The new Defense Independent ERA.
DIPR=The Defense Independent Pitching Rating. A calue equaling defense
independent earned runs over replacement value.
DIFF=The difference between the defense independent earned run total
and the pitchers actual earned run total. A positive rating means the
DI ER is lower than actual earned runs. A negative value indicates the
The ratings for every single pitcher in the majors last year will be
posted on the web in a day or so. These numbers will look like
complete Traditional Pitching lines with Wins, Losses, ERA, IP, H, HR,
BB, SO, ER and the above DIPR. They are sorted by team and within
teams are sorted from highest DIPR to lowest. They will be posted at:
Stay tuned for a post on the "Top 20" DIPRs in the majors last year.
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