VORP: Introduction for 2001
Keith Woolner
The VORP reports return for 2001! There's been some substantial
revamping this year, and while I think everything is accurate, I
still may be fixing bugs for awhile (i.e. consider these reports
"beta" for awhile). If you notice something that seems amiss,
please let me know, and I'll check into it.
I'm also going to be experimenting with the format of the
updates I post on the newsgroups. While the reports on the web
site will have more information per player, I am considering
posting weekly updates for all players to the newsgroups, rather
than just the top/bottom 20 as I did last year. Feedback and/or
constructive criticism are welcomed.
-- Keith
----
VORP (Value Over Replacement Level) is a sabermetric analysis
that seeks to measure the contribution, in runs, of a player beyond
what a backup (or replacement-level) player would produce for an
average team given the same amount of playing time. VORP is adjusted
for park and league, and position (for non-pitchers).
A full description of VORP, along with the complete and updated VORP
figures for the season to date, can be found in the Stathead Baseball
Engineering Library at http://www.stathead.com
New for 2001:
Due to the demise of the STATS BBS, I've had to switch to a
different source of box scores, which unintentionally gave me
the opportunity to rewrite the code that extracts data from the
box scores, allowing more complete tracking during the season.
As a result, there have been several improvements to the way VORP
is figured this year. The following is a mostly complete list
of the changes I've made to VORP reports for 2001:
* OBP computation now includes HBP and SF
* Each player's positional average is now weighted for games at
multiple positions, rather than using just his most frequent
position.
* The VORP report at Stathead.com has additional columns (longer than
would fit comfortably in a Usenet article posting. Among the new
columns are a batter's percentage of team PA, Positional and
Replacement-level rates of production (PMLVr and RPMLVr), and
seasonal total MLV, PMLV, and RPMLV
* The full pitchers VORP report on the web site now shows blown
saves, holds and park-adjusted RA, and runs prevented (compared
to an average pitcher).
Legend for the VORP reports:
VORP -- (V)alue (O)ver (R)eplacement (P)layer. The number
of runs contributed beyond what a replacement-level
player would contribute if given the same percentage
of team plate appearances.
VORPr -- VORP rate. Runs/game contributed beyond what a replacement
level player would produce. Also a rate stat.
MLVr -- (M)arginal (L)ineup (V)alue (r)ate of production
Basically, the number of runs per game the batter
contributed to a league average team beyond what
a league average hitter would produce. This is a rate
stat similar to OPS. The comparable season total is MLV.
PMLVr -- Positional MLV rate. Runs/game contributed by
a batter beyond what an average player at the same
position would hit in a team of otherwise league-average
hitters. Like MLVr, it is a rate stat. The comparable
season total is PMLV.
RPMLVr -- Replacement level MLV rate. Runs/game contributed by a
batter beyond what a replacement level player at the same
position would hit in a team of otherwise league-average
hitters. The comparable season total is RPMLV. It differs
from VORPr and VORP only in that it is solely based on
batting performance whereas VORP includes basestealing.
PkRA -- A pitcher's park-adjusted RA, expressed on a scale
like ERA or RA.
RA+ -- Park and league normalized Run Average. Similar to ERA+
found in Total Baseball, but based on RA rather than ERA.
In setting the positional average and replacement level averages
for each player, every game and position that the player appeared
in is weighed into the equation. E.g. if a player played 20 games
at shortstop and 20 games at third base, his positional average
would be halfway between the average SS and 3B production. Pinch
hitting and pinch running appearances are compared to the PH/PR
league averages as well.
A player is listed at the position he appeared most often at.
In the case that two or more positions are tied for the most
games, the player is listed multiple times (once at each position).
However, unlike last year, his positional average is a composite
of all of his actual positional appearances, rather than just the
most frequent, so his actual VORP should not change across the
several listings. This is arguably a minor bug that I may clean up
at some point during the year.
Replacement-level delta is set at 70 points of OPS below league
positional average (based on previous studies I've done, but have not
published -- I may get around to it this year). The same delta is
used for all positions (this is a possible area for future research).
For pitchers, VORP is defined as the number of runs a pitcher
surrenders below what a replacement level pitcher would have
given up in the same number of innings. Replacement level is
set at +1.00 above the league average RA.
Park factors being used are the 3-year park factors (for 1998-2000)
reported in the 2001 STATS Major League Handbook.
The latest VORP reports for the current season are available for
hitters and pitchers in the Stathead Library at
http://www.stathead.com/
--
Keith Woolner ke...@woolner.com http://www.woolner.com
Baseball Engineering Library, http://www.stathead.com
List Owner, Red Sox mailing list, http://www.woolner.com/redsox/list
Newsgroup Moderator, rec.sport.baseball.analysis
Author, Baseball Prospectus 2001 http://www.baseballprospectus.com