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Fantasy Baseball Analytics: An Update on Stuff-ERA

Several months back I created a new era estimator that I called Stuff-ERA. The model was built using a series of models that use pitch location to determine several different pitch results. This then allowed me to extract each pitcher’s individual influence on these various results. All of these factors were passed in a model to help estimate what their talent level suggested their ERA should have been. Recently I made a few small updates to the model for wOBA.

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Update One – Park Factors

After looking over the model, I realized that while I was factoring in the pitcher and hitter for each of the different pitchers and hitters I was missing a major influence on wOBA, the field. So in order to do this, I added an additional fixed effect to my random-effects model for Home Team.

The idea was to see if certain pitchers were being hurt in the model due to their own skills or if their home park was influencing them as well. Below is the Park adjustment for all 30 MLB Stadiums in 2019.

Home TeamImpact

Unsurprisingly, Coors Field tops the list as the worst park for pitchers, with the model viewing Busch Stadium as the most pitcher-friendly park in all of baseball. This is solely in terms of wOBA but there could be other factors outside of the park factors themselves that we are not accounting for. This could be a function of defense as well.

Update Two – xwOBA Model

Something that I alluded to in my Plate Discipline piece earlier this week was a small change to the underlying xwOBA model. Overall the change is a very small one, but it did cause small changes to the individual pitcher’s wOBA Influence. Overall, the changes to the leaderboard are small as it led to some shuffling near the top and some small adjustments to final Stuff-ERA. In the end, this was more of a cleanliness impact as it did not adjust the overall correlation between Stuff-ERA and actual ERA.

Updated 2019 Stuff-ERA Leaders

This is a quick post with not a ton of new and exciting information so I will leave the top 100 pitchers from 2019 (min 1500 pitches thrown) according to Stuff-ERA. Once again the model still is in love with Luis Castillo and I think he takes the step to true Ace Status in 2020.

Luis Castillo2.36
Stephen Strasburg2.83
Sonny Gray2.88
Patrick Corbin2.94
Jack Flaherty2.95
Gerrit Cole2.96
Jacob deGrom2.99
Mike Soroka3.00
Mike Clevinger3.02
Justin Verlander3.04
Charlie Morton3.08
Kenta Maeda3.11
Lucas Giolito3.24
Lance Lynn3.31
Zack Greinke3.37
Dakota Hudson3.41
Blake Snell3.42
Walker Buehler3.47
Hyun-Jin Ryu3.47
Yu Darvish3.50
Max Scherzer3.50
Felix Pena3.54
Clayton Kershaw3.56
Sandy Alcantara3.56
Mike Minor3.57
German Marquez3.59
Aaron Nola3.66
Marcus Stroman3.70
Shane Bieber3.72
Jake Odorizzi3.73
Jeff Samardzija3.74
Anibal Sanchez3.74
Griffin Canning3.75
Brad Keller3.75
Joey Lucchesi3.81
Yonny Chirinos3.81
Chris Paddack3.87
Julio Teheran3.89
Chris Bassitt3.89
James Paxton3.89
Domingo German3.90
Brett Anderson3.93
Andrew Cashner3.93
Eduardo Rodriguez3.93
Chris Sale3.94
Pablo Lopez3.94
Mike Fiers3.95
Noah Syndergaard3.95
Ryan Yarbrough3.98
John Means3.99
Kevin Gausman4.00
Cole Hamels4.01
Spencer Turnbull4.01
Trevor Bauer4.02
Jon Gray4.02
Kyle Hendricks4.03
Madison Bumgarner4.05
Adrian Houser4.07
Jose Berrios4.08
Brandon Woodruff4.08
Max Fried4.09
Zack Godley4.12
Zack Wheeler4.14
Chris Archer4.15
Andrew Heaney4.16
Zach Plesac4.17
Chase Anderson4.17
Homer Bailey4.19
Anthony DeSclafani4.20
Trevor Richards4.20
Zach Davies4.21
Dylan Bundy4.22
Wade Miley4.23
Joe Musgrove4.25
Brad Peacock4.26
Dallas Keuchel4.28
Kyle Gibson4.28
Jason Vargas4.30
Trent Thornton4.32
Michael Pineda4.32
Tyler Beede4.34
Merrill Kelly4.35
Danny Duffy4.36
Caleb Smith4.37
Daniel Norris4.38
Freddy Peralta4.39
Mike Foltynewicz4.40
Martin Perez4.42
Steven Brault4.42
Cal Quantrill4.43
Trevor Cahill4.43
Robbie Ray4.44
Miles Mikolas4.49
Marco Gonzales4.50
Zach Eflin4.61
Matthew Boyd4.61
Eric Lauer4.62
Jake Arrieta4.63
Steven Matz4.66
Tyler Mahle4.68

After looking over the list who do you think Stuff-ERA is too high on and who is it underestimating?

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