from Amazon
Thursday, August 19, 2010
The greatness, or not, of Josh Hamilton
Poz asks, and he’s a bit bothered with the fielding analysis part:
Fangraphs shows Hamilton as having (by a sizable amount) the highest WAR among position players in baseball at 6.7. ... However, Baseball Reference does not show Hamilton in the Top 5 at all....
So what gives? Tom Tango explains that the big difference is how the the competing WARS rate defense. Fangraphs’ WAR uses Ultimate Zone Rating to quantify defense. Baseball Reference’s WAR uses Total Zone to quantify defense. Tom thinks “UZR is better, but not markedly so.”
In Hamilton’s case, the competing systems judge him almost precisely the same on the offensive side. Fangraphs has him at +47 runs, Baseball Reference at +46 runs. The difference is defense. UZR has Hamilton as a very good defender — his UZR is +5.8.* Total Zone has Hamilton as a below average field, minus-7 runs.
Those 13 runs on defense make up the difference.
...
Tom Tango does not have a strong feeling about which WAR is more accurate (“Split the difference,” he suggests).
For those interested, here was the full email response I had given Poz:
Joe,
I have a thread here that talks about the differences:
http://www.insidethebook.com/ee/index.php/site/comments/mail_rwar_v_fwar/
But, let me just give you some highlights. First off, I like both because they both follow my framework. Which is to say, they do offense as relative to the average hitter, defense relative to the average at his position, they apply a positional adjustment, and add in replacement level. So, they both follow that.
The big difference is that Fangraphs relies on UZR, while B-R.com relies on Total Zone. UZR is better, but not markedly so. Therefore, the best thing to do is really split the difference. Ok, now let me take a look at Josh Hamilton to see what the story is. Be back in a sec…
Ok, just what I thought. If you go here:
http://www.baseball-reference.com/players/h/hamiljo03.shtml#batting_value
And here:
http://www.fangraphs.com/statss.aspx?playerid=1875&position=OF#value
We see that the offense is +46 runs for one, and +47 runs for the other. The positional adjustment is -4 runs in both. Replacement level (which really mean playing time) is +16 for one and +17 for the other. The difference is fielding: UZR has him at +6 and Total Zone at -7. That’s a 13 run difference or 1.3 wins, which pretty much explains almost all the difference.
For what it’s worth, his fielding+position in 2009 UZR was +5 runs and his Total Zone in 2009 was +7. Whether it’s more believable that his was +5 and then +6 in UZR, or +7 then -7 in TZ is a judgement call. I find that the best thing to do is split the difference. No fuss, no muss, and best of all, you are half right, rather than possibly being all-wrong.
Tom