Introducing JustVORP

One of the most popular sabermetric statistics ever invented is VORP, Baseball Prospectus' measure of offensive value over replacement player.  Not only does it measure offense, it compares each player to his positional peers, because a catcher with an .800 OPS is much more valuable than a first baseman with an .800 OPS.  We've all gotten a lot of mileage from VORP over the years, so kudos to Keith Woolner and BPro for that.

But VORP also has its flaws:

1. It's based on Equivalent Average MLV, which underrates walks.
2. It doesn't account for league quality.
3. It defines replacement-level in a funky way.  80% of league-average RC/out isn't a bad choice (although it's slightly high), but that number changes to 85% for catchers and 75% for 1B and DH.  Why?  Uh...  good question.  VORP ends up overrating 1B/DH's and underrating catchers.
4. It uses offensive averages to define the defensive spectrum instead of actual differences in defensive value.  Why is that a mistake?  Because it makes DH look like a tougher position to play than 1B and LF/RF, since DHs hit worse as a group.  And also because you'll get seasons like 1961 when CFs outhit LFs.  Do we really think CF is an easier position to play when that happens?  No.

Fortunately, mere mortals can come along and stand on the shoulders of the giants before them.  Justin is one of those mortals, and for the past year he has calculated the statistics necessary to produce a better version of VORP.  I'm going to call it JustVORP.  Conveniently, it solves all the problems listed above:

1. It's based on park-adjusted linear weights, derived from BaseRuns.
2. It accounts for the talent difference between the AL and NL.
3. It defines replacement level as 73% and 78% of league-average offense (depending on league).  That number ignores position, because...
4. It uses the proper defensive spectrum, based on relative difficulties of playing each position.  And the position adjustment is added in after the offensive component is calculated.  Offense is offense, but it has more value depending on the position it comes from.

As a reminder, here are the position adjustments over a full season:

CA: +12.5 runs

SS: +7.5 runs

2B/3B/CF: +2.5 runs

LF/RF: -7.5 runs

1B: -12.5 runs

DH: -17.5 runs

Now, like VORP, JustVORP is obviously missing a significant piece of the puzzle, namely fielding relative to position.  But that's half the beauty -- with the wide variety of fielding metrics available, you can pick the one you're most comfortable with, like UZR.  Or average some together.  Or use the Fans Scouting Report.  Or use 2009 projections.

Click here to download full 2008 JustVORP data, complete with a pivot table ready to help you slice and dice.  Here's the top twenty-five: