The world according to VORP

Twenty years ago, if you mentioned "on-base percentage" you had to explain it. Or maybe not. It's pretty self-explanatory. But you had to wink to reassure everyone that you didn't really buy into such nontraditional claptrap.

Ten years ago, if you mentioned "OPS" you had to explain it, usually by placing "on-base plus slugging percentage" inside parentheses.

A lot has happened since then. Today there are only a few front offices that don't value on-base percentage, and there are only a few baseball writers who refuse to even acknowledge the possibility that batting average isn't the best measure of a batter. But of course, time marches on. There are always new statistics being invented, and there are always teams and writers and fans looking for whatever edges they can find.

These days, many of them are turning to a sophisticated little contraption called VORP: Value Over Replacement Player.

Sounds simple enough, doesn't it?

But of course the devil is in the details, and there are a great number of details involved in determining both "value" and "replacement player." Let's go with value first, because everything follows from that. Actually, first let's meet Keith Woolner, VORP's inventor.

"I didn't grow up reading Bill James," Woolner says. "I actually first became aware of the sabermetric community on the Usenet newsgroup rec.sport.baseball in the late '80s, when I was in college. I played around with stats on my own, and in the mid-1990s I started working on what would eventually become VORP. After several false starts, and debating what it was I wanted to actually measure, I was able to settle on a few important points, which guided VORP's development."

Woolner wanted something that could naturally adjust to changing environments; a stolen base, for example, has a different value in 1906 than in 2006. He wanted to account for the likelihood that an average player who plays in 150 games is more valuable than a great player who plays in 50 games (something that doesn't come across if every player is measured against "average"). And Woolner wanted to account for the fact that there aren't as many players capable of playing, for example, shortstop as there are players capable of playing first base. It follows, then, that if a shortstop and a first baseman have identical batting stats, the shortstop is almost certainly more valuable than the first baseman. Of course, Woolner needed to adjust for the impact of different ballparks, too.

And what is the definition of "replacement player"? That's always going to be a somewhat arbitrary decision. In this case, the short answer is that Woolner defines a "replacement" hitter as being roughly 80 percent as good as an average major league hitter at his position (the number actually varies somewhat, depending on the position).

To measure fundamental offensive production -- and there's VORP for pitchers, too -- Woolner began with Bill James' seminal runs created, but came up with a modification that's served him well. The result is a number, a player's VORP, that measures his value in runs. Despite missing a couple of weeks last season, Albert Pujols topped the majors with an 85.4 VORP, which means he was, strictly in terms of hitting (and base stealing) 85.4 runs better than a replacement-level major league first baseman. Simple as that.

Some years ago, Baseball Prospectus adopted VORP as one of the site's signature statistics, and the rest is semi-history. As Woolner says, "I knew VORP had really 'made it' when I heard John Kruk make fun of it on 'Baseball Tonight,' and later when it got mentioned in The Onion. When something is well-recognized enough to be ridiculed, you know it's hit the mainstream."

Now, you might be wondering (as I did), "Why would teams settle for an offense-only statistic, when Baseball Prospectus also publishes WARP -- Wins Above Replacement Player -- which does factor in not only defensive position, but also defensive performance?"

It's a real good question. The answer is that when it comes to defense, nobody trusts anybody. The teams that really buy into objective analysis have their own, proprietary (i.e. secret) methods for measuring defense. And the teams that don't buy into objective analysis simply believe what their scouts tell them. Either way, teams pay little attention to Baseball Prospectus' fielding runs, or Baseball Info Solutions' +/- system, or any of the other metrics we sometimes bandy about (this is changing, but at a pre-fossil fuels glacial pace).

Another nice thing about VORP: Unlike most of the fielding systems, and hitting systems too, the underlying methodology for VORP is available to anybody who wants to look under the hood and perhaps do a bit of tinkering. In addition to the modification referenced earlier, there's a primer on VORP in the 2002 edition of Baseball Prospectus (the book), which is still available via your better Web-based booksellers.

Meanwhile, the actual numbers for all major leaguers dating back to 1959 can be accessed at Baseball Prospectus (the Web site), both hitters and pitchers. VORP never will be a household acronym, nor should it be. Baseball analysts have worked too hard for one method to dominate all others, and they're only going to work harder. But the truth is that when it comes to hitting, most of the heavy lifting has already been done, the low-hanging fruit already plucked. VORP and similar methods are plenty good enough for the job, and enterprising young sabermetricians are best advised to turn their intellects to more mysterious subjects, such as young pitchers and Derek Jeter's Gold Gloves.

Senior writer Rob Neyer writes for Insider three times most weeks during the season. You can reach him via rob.neyer@dig.com, and his new book, "Rob Neyer's Big Book of Baseball Blunders," is available everywhere.