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# League Leaders in ERA Estimators

Two stats I've been interested in recently are bbFIP and kwERA.  These ERA estimators were created by Tom Tango as simple alternatives to FIP by using different components.  bbFIP (batted ball fielding independent pitching) is used with strikeouts, walks, and batted ball types only (ground balls, fly balls, line drives, and pop ups).  kwERA (strikeout-walk earned run average) is even simpler - its only inputs are strikeout and walk totals.  Both metrics are slightly better than FIP at predicting future ERA performance (here is the link to the post at Tango's blog with the discussion on correlations in the comments section).  I recently added these to my player pages with MLBAM data; in this post, I will show the leaders and trailers in 2010 for both metrics.

This is Tango's equation for bbFIP:

### (((11*((BB+LD)-(K+PU)))+(3*(FB-GB)))/PA)+C

in which K is strikeouts, BB is unintentional walks and hit by pitches, GB is ground balls, FB is fly balls, LD is line drives, PU is pop-ups, PA is plate appearances, and C is the coefficient to align to the league average ERA.

Tango says, "A line drive is like a walk, an infield fly is like a strikeout, and the gap between an outfly and a groundball is about one-fourth the gap between BB and SO."  I calculated the coefficient from Baseball Prospectus data, and I get 4.62 as the American League coefficient and 4.66 as the National League coefficient (scaling to 4.14 ERA in the AL and 4.03 ERA in the NL).  Please take note that I'm using MLBAM data here, so batted ball classifications will be slightly different from the ones from BPro that I used to calculate the coefficients, so there should be a tiny difference in the values shown here than the ones calculated directly from BPro.  I'll present the data in two tables: the first shows the 15 and leaders and trailers in bbFIP among pitchers with at least 200 but less than 500 opposing plate apperances, and the second one shows the data for pitchers with at least 500 opposing plate appearances.

 Rank Pitcher Team bbFIP 1 Joaquin Benoit Rays 1.28 2 Billy Wagner Braves 1.36 3 Hong-Chih Kuo Dodgers 1.50 4 Rafael Betancourt Rockies 1.71 5 Takashi Saito Braves 1.89 6 Matt Thornton White Sox 1.98 7 Sergio Romo Giants 2.05 8 Brian Wilson Giants 2.12 9 Ryan Madson Phillies 2.19 10 J.J. Putz White Sox 2.33 11 Stephen Strasburg Nationals 2.33 12 Joel Hanrahan Pirates 2.34 13 Edward Mujica Padres 2.44 14 Neftali Feliz Rangers 2.47 15 Luke Gregerson Padres 2.48 1x Dontrelle Willis Tigers / Diamondbacks 6.13 2x Oliver Perez Mets 5.90 3x Brad Lincoln Pirates 5.78 4x Casey Coleman Cubs 5.78 5x Dana Eveland Blue Jays / Pirates 5.73 6x David Huff Indians 5.70 7x Dusty Hughes Royals 5.62 8x Chris Tillman Orioles 5.60 9x Ian Snell Mariners 5.52 10x Lance Cormier Rays 5.31 11x Kyle Lohse Cardinals 5.30 12x Dustin Nippert Rangers 5.28 13x Aaron Laffey Indians 5.26 14x Jesse Litsch Blue Jays 5.25 15x Jeff Suppan Brewers / Cardinals 5.24

 Rank Pitcher Team bbFIP 1 Jered Weaver Angels 2.66 2 Hiroki Kuroda Dodgers 2.81 3 Mat Latos Padres 2.83 4 Francisco Liriano Twins 2.99 5 Cliff Lee Mariners / Rangers 3.00 6 Adam Wainwright Cardinals 3.01 7 Cole Hamels Phillies 3.06 8 Roy Halladay Phillies 3.06 9 Colby Lewis Rangers 3.09 10 Clayton Kershaw Dodgers 3.09 11 CC Sabathia Yankees 3.12 12 Roy Oswalt Astros / Phillies 3.17 13 Felix Hernandez Mariners 3.19 14 Josh Johnson Marlins 3.21 15 Jon Lester Red Sox 3.23 1x Ryan Rowland-Smith Mariners 5.76 2x Scott Kazmir Angels 5.28 3x Kyle Kendrick Phillies 5.15 4x John Lannan Nationals 5.15 5x Dave Bush Brewers 5.09 6x Aaron Harang Reds 5.04 7x Livan Hernandez Nationals 5.03 8x Carlos Zambrano Cubs 4.99 9x Paul Maholm Pirates 4.98 10x Scott Feldman Rangers 4.98 11x Joe Saunders Angels / Diamonbacks 4.90 12x Brian Bannister Royals 4.89 13x Tom Gorzelanny Cubs 4.87 14x Rodrigo Lopez Diamondbacks 4.87 15x Craig Stammen Nationals 4.84

Yes, the Phillies are going to be scary next year.

The formula I'm using for kwERA is C-(12*(K-BB)).  The coefficients are 5.22 for the AL and 5.28 for the NL.  You'll see a lot of the same names that were on the bbFIP leaderboard.

 Rank Pitcher Team kwERA 1 Rafael Betancourt Rockies 1.27 2 Billy Wagner Braves 1.58 3 Joaquin Benoit Rays 1.65 4 Matt Thornton White Sox 1.98 5 Stephen Strasburg Nationals 2.01 6 Takashi Saito Braves 2.32 7 Edward Mujica Padres 2.33 8 Luke Gregerson Padres 2.35 9 Carlos Marmol Cubs 2.37 10 J.J. Putz White Sox 2.40 11 Hong-Chih Kuo Dodgers 2.42 12 Joel Hanrahan Pirates 2.42 13 Ryan Madson Phillies 2.49 14 Brian Wilson Giants 2.51 15 John Axford Brewers 2.57 1x Dontrelle Willis Tigers / Diamondbacks 5.74 2x Dana Eveland Blue Jays / Pirates 5.70 3x Oliver Perez Mets 5.70 4x Jason Marquis Nationals 5.37 5x Lance Cormier Rays 5.31 6x Brad Thomas Tigers 5.30 7x Jesse Litsch Blue Jays 5.28 8x Sean Gallagher Padres / Pirates 5.28 9x Blaine Boyer Diamondbacks 5.28 10x Chris Tillman Orioles 5.22 11x Aaron Laffey Indians 5.22 12x Casey Coleman Cubs 5.19 13x Brian Moehler Astros 5.18 14x Jamey Wright Indians / Mariners 5.18 15x Ian Snell Mariners 5.17

 Rank Pitcher Team kwERA 1 Cliff Lee Mariners / Rangers 2.84 2 Jered Weaver Angels 2.86 3 Mat Latos Padres 3.01 4 Roy Halladay Phillies 3.06 5 Josh Johnson Marlins 3.10 6 Tim Lincecum Giants 3.17 7 Cole Hamels Phillies 3.22 8 Adam Wainwright Cardinals 3.23 9 Francisco Liriano Twins 3.24 10 Ricky Nolasco Marlins 3.24 11 Brandon Morrow Blue Jays 3.27 12 Dan Haren Diamondbacks / Angels 3.29 13 Roy Oswalt Astros / Phillies 3.32 14 Yovani Gallardo Brewers 3.36 15 Felix Hernandez Mariners 3.36 1x Ryan Roland-Smith Mariners 5.22 2x Scott Kazmir Angels 5.17 3x Aaron Cook Rockies 5.07 4x Mitch Talbot Indians 5.02 5x Nick Blackburn Twins 4.86 6x Armando Galarraga Tigers 4.86 7x John Lannan Nationals 4.83 8x Paul Maholm Pirates 4.81 9x Brad Bergesen Orioles 4.79 10x Scott Feldman Rangers 4.73 11x Brian Bannister Royals 4.73 12x Kyle Kendrick Phillies 4.72 13x Vin Mazzaro Athletics 4.69 14x Mike Pelfrey Mets 4.68 15x Chris Volstad Marlins 4.66

I will reiterate that the Phillies will be scary next year.  Also, I must say that I didn't realize just how good Mat Latos is.

I find both metrics to be extremely intriguing.  The thing that makes me more wary of bbFIP than of FIP or xFIP is that it uses line drives and pop ups as inputs; they don't normalize as quickly as ground ball and fly ball rates, so (as always), be careful about small sample sizes.  I'd like to expand the data to the past three years so we can get a better feel for line drive and pop up skill.  As for kwERA, I wish people would start using it, or even just (K-BB)/PA, instead of K/BB.  Tango has shown that K-BB is superior to K/BB in terms of measuring run prevention.

For now, here is a spreadsheet with bbFIP and kwERA stats for all 635 pitchers in 2010 along with the total number of batters that each pitcher faced.  For pitchers who pitched in both leagues, I'm weighting their averages by batters faced in each league.

The data in this post are courtesy of Joe Lefkowitz's PITCHf/x tool and Baseball Prospectus.