So, I was just out at the Sloan Sports Analytics Conference in Boston … and it was awesome, as you might expect. I’ll have more to say about the overall conference in the next couple of days, but there were baseball tidbits that I thought some of you might find interesting and will try to post throughout the day.
OK, so it’s no secret that I’m a big fan of the statistical concept of Wins Above Replacement (WAR). I like the idea of trying to find a number that can give us a rough idea of how much a player contributes to his team. I like the idea of gathering a player’s production as a hitter, base runner and fielder and trying to estimate how many extra wins he adds (or takes away). I like the idea of trying to isolate a pitcher’s contribution to a team. It’s an imperfect but utterly fascinating statistic now and it will get better over time. I love baseball more because of WAR.
There are several versions of WAR out there – most prominently at Baseball Reference and at Fangraphs — and this has been an issue for many people, even those open to new statistics. They will say, “How can WAR be a good statistic if people figure it differently? How can I put any stock in a statistic if the Fangraphs version of it has Chase Headley as being 7.5 wins above replacement while Baseball Reference has him six wins above replacement?”
There are a few different answers to this. The main one — explained well by the Sam Miller in a good piece at ESPN the Magazine — is that baseball is a complicated thing … and complicated things do not lend themselves to clean and easy answers. Fangraphs WAR is figured differently from Baseball Reference WAR — especially for pitching and defense — because people at Fangraphs and Baseball Reference have different beliefs about the best way to measure players. They like their individual methods. And it so happens that their individual methods will sometimes come to surprisingly divergent conclusions (though, more often than not, the two are in basic agreement).
I think one thing about embracing advanced statistics is that you just have to be open to a little bit of chaos. Sure, batting average will give you the same answer every time. But bating average isn’t a very telling statistic.
I will say, though, do think it would be better for everyone if the B-Ref and Fangraph versions came somewhat closer together. I don’t mean they should change the way they measure players. I’m just saying that their methods are more similar than different, and it would be great for them to find common ground where common ground can be found.
Well, it seems like they might — MIGHT — be coming a little closer together in an important way. I ran into the brilliant Sean Forman at the Sloan Conference and he told me something — apparently Fangraphs and Baseball Reference have a slightly different idea of what constitutes replacement level. As you already know, WAR measures players against a fictional “replacement player,” who is supposed to represent the sort of player a team could easily acquire from the minors or on the waiver wire.
I didn’t know that Fangraphs and Baseball Reference had slightly different replacement levels. It’s a very small difference, but very small differences in a statistic like this — which is figured to a tenth of a point — are very important.
Sean told me that, for instance, Baseball Reference WAR and Fangraphs WAR have very similar views on the production of Jack Morris. The two figure pitching in different ways — with Fangraphs relying a lot on walks, strikeouts and home runs while Baseball Reference gives significance to runs allowed — but Sean said their numbers should, more or less, line up. They don’t.
Fangraphs has Morris being worth 56.9 wins above replacement. Baseball Reference has him at 39.3 WAR.
Forman says almost the entire difference is based on the value the two groups give a replacement player.
And so, good news, he says that he intends to meet with Fangraphs folks and try to hammer out a consistent value for replacement level. He said they might try to get Tom Tango and others involved too. I think this would be great news for the statistic. It’s a fine thing for Fangraphs WAR and Baseball Reference WAR to be different. But it would be great if they could start in the same place.