Tuesday, July 20, 2010
Pitchers’ wOBA Against, 2010Posted by JT Jordan
Batting Average Against is commonly cited in mainstream analysis as an indicator of how hard a pitcher has been hit. This is blatantly incorrect, of course, as batting average treats all hit types the same- so a pitcher that has allowed predominantly singles is seen as more or less the same as a pitcher who allows a standard distribution of singles, doubles, triples, and home runs. Furthermore, we're also looking at a rather limited analysis- what about other baserunners allowed, via the walk? How about on-base percentage against?
Well, that's a step up. But we're still dealing with the issue of all hits being treated the same. So, we're not all the way there. Slugging percentage accounts for hit types, but the weighting is rather awkward- if you're relatively familiar with run expectancy, you'll know that a home run isn't worth two doubles. A double isn't worth two singles. A triple isn't worth three singles, and...well, you get the picture. So, adding both on-base percentage and slugging percentage- otherwise known as OPS- will give us a reasonable estimate, but not as thorough as we'd like. And that's not even taking into consideration the fact that we're adding two rates with different denominators, and...well, it's pretty ugly. We can do better.
That "better," of course, is Weighted on Base Average (wOBA). wOBA assigns the proper marginal value to each event (linear weight values) and transforms the coefficients to turn it into a rate that matches league on-base percentage. No more awkward weighting for hit types and walks, and we can sprinkle in other events such as reaching on an error, stolen bases/caught stealing, and strikeouts (which make for a tiny, almost insignificant difference). So, which pitchers have the best and worst wOBA against so far in 2010?
First, the National League (minimum 100 IP, league average = .330):
Name wOBA Mat Latos 0.247 Josh Johnson 0.251 Adam Wainwright 0.263 Ubaldo Jimenez 0.264 Tim Hudson 0.286 Roy Oswalt 0.287 Tim Lincecum 0.288 Clayton Kershaw 0.289 Johan Santana 0.289 Roy Halladay 0.294
The Pads' Latos leads the National League with an extremely low .247 wOBA. The rest of this list is comprised of more or less the usual suspects. The worst? Oh, they're bad:
Name wOBA Mike Leake 0.344 Ricky Nolasco 0.345 Dan Haren 0.349 Kyle Kendrick 0.352 Aaron Harang 0.356 Paul Maholm 0.357 Wandy Rodriguez 0.363 Randy Wolf 0.363 David Bush 0.367 Rodrigo Lopez 0.371
Haren's the biggest surprise to me in this list, as he's been one of the better pitchers in the National League the past couple of years. He didn't have a very good first half, but here's to hoping that he sees a turnaround in the second half. The rest of the list isn't exactly filled with guys you'd shell humongous contracts to, but you knew that already.
Now, the American League (Minimum 100 IP, league average = .327):
Name wOBA Cliff Lee 0.256 Jon Lester 0.273 Trevor Cahill 0.278 John Danks 0.281 Felix Hernandez 0.284 Jered Weaver 0.286 Colby Lewis 0.287 CC Sabathia 0.291 Justin Verlander 0.291 Phil Hughes 0.292
Boy, the Rangers sure got themselves a bona fide ace in Lee. It's nice to see a few surprises in this list, such as the Athletics' Trevor Cahill- who's having a solid season thus far, and the Rangers' Colby Lewis, who has seemingly reinvented himself since his two-year stint in Japan.
Name wOBA Ben Sheets 0.352 Joe Saunders 0.354 Kevin Slowey 0.356 Tim Wakefield 0.358 John Lackey 0.361 A.J. Burnett 0.367 Brian Bannister 0.368 Scott Feldman 0.369 Kevin Millwood 0.373 Nick Blackburn 0.405
I don't think the A's are going to get a lot in return for Sheets, unless the team vying for his services believes he can pitch like he used to a few years ago. Two big names highlight this list from the Red Sox and Yankees, as expensive starters A.J. Burnett and John Lackey are getting knocked around quite a bit. Twins starter Nick Blackburn, in the meantime, has been hit as if every batter he's faced is Hank Aaron.
One of the beauties of wOBA is that it can easily be disassembled back in to linear weights; expressed as runs above or below the average player. This is often referred to as "wRAA" (for Weighted Runs Above Average) on Fangraphs. I've park-adjusted the wOBA using Baseball-Reference's 3-year park factors, and converted it back into LWTS. Your leaders:
Name LWTS Josh Johnson 33 Ubaldo Jimenez 31 Adam Wainwright 30 Jon Lester 27 Cliff Lee 22 Mat Latos 22 John Danks 20 Tim Lincecum 20 Roy Halladay 19 Felix Hernandez 18
This helps puts things into perspective a bit. While it is true that Lee has the lower wOBA against than the Sox's Lester, Lester's also accumulated about 27 more innings. The worst pitchers?
Name LWTS Scott Kazmir -18 Kevin Millwood -19 A.J. Burnett -19 David Huff -22 John Lannan -22 Charlie Morton -22 Brad Bergesen -23 Zach Duke -24 Nick Blackburn -30 Ryan Rowland-Smith -32
Of course, the typical caveats apply: this is by no means a perfect measurement of pitcher valuation; simply just another way of assessing a pitcher. All data for 2010 (through July 19th) can be found here. I've supplied the non park-adjusted wOBA, as I realize that some people will undoubtedly want to toy with it using other park factors of their choice.
JT Jordan is an avid Giants fan and runs a blog at Triples Alley. He can be reached at firstname.lastname@example.org.