I wanted to highlight Pitcher over and under performers. Naturally, Mike Podhorzer has already done that and more concisely and eloquently than I ever could. In conjunction to what he did (ERA vs. SIERA within this year), I wanted to look at pitchers’ skills and luck relative to last year.
By “skills” I mean K%-BB%, combined Contact% and SwStr%, GB/FB and IFFB%. These columns are in green.
By “luck” I mean BABIP, LOB% and HR/FB. These are in some emotional shade of red.
I took all the 2014 vs. 2013 differentials and z-scored them. I summed them up and presented them under column 3 (“SKILL”) and column 4 (“LUCK”). In short, these are not their skill and luck scores for 2014, but their change relative to 2013…in relation to how much everyone else from this list changed (50 IP qualifier).
The grid below is initially ordered by their Skill + Luck Scores:
Scroll to the right for their differentials in each category (columns in white) and differential z-scores (in green/emotional red). You can click on the tab prior to the presented tab in order to see the 2013 and 2014 raw data. You can sort the grid by skill and score or even the ERA-SIERA differential (column 2), which reflects the amount of ERA differential change from 2013 to 2014. For example:
2013 Kelvin Herrera: 1.53ERA; 3.63SIERA; -2.09ERA differential
2014 Kelvin Herrera: 3.86ERA; 2.5SIERA; +1.36ERA differential
Last year, Kelvin Herrera had a +1.36 run differential. While his ERA was 3.86, his SIERA was 2.5. This year, his ERA is 1.53, but his SIERA is 3.62 for -2.09 run differential. In relation to everyone else, this had a 3.45 z-score. Unsurprisingly, Clay Buchholz is on the opposite side of the spectrum to the same degree (-3.45 z-score).
For further clarification, because I’m sure this content and this grid will baffle you (because of my semantics and not your competence level), those who rank highest in “Luck” had the most change in BABIP, LOB% and HR/FB relative to last year. Wade Davis, Brandon League, Kelvin Herrera, Roberto Hernandez, Jonathan Papelbon, Jake McGee and Garrett Richards makeup the top 7 from this category. However, if we filter by “Skill”, Wade Davis ranks #1 here as well. Garret Richards finds himself at #31. Naturally, along with Kelvin Herrera, they both rank very highly in the ERA differential change: Wade Davis is #7 overall and Garret Richards is #23 overall.
This list, albeit through z-scores, gives us a depiction on why their ERA differentials changed relative to last year – through skill and/or luck.
A few targets on both sides of the spectrum (Filter the “Sk+Lu” Column and attend to those hovering around 0.00):
Baffled? That’s understanding. Not Baffled? You win, and feel free to sell high on Adam Wainwright.
Daniel Schwartz contributes for RotoGraphs when he's not selling industry leading thermal packaging. You can follow him on twitter @RotoBanter