The Change: Arsenal Scores

The theory first. By looking at the results on a per-pitch level, we can spot pitchers that have somehow been worse than the sum of their parts to date. Those pitchers, with better sequencing and selection of their existing pitches, or just luck, could be better in the future.

In order to avoid the problems inherent in balls in play data, we’re going to focus on two classes of information that help us the most — ground balls and strikeouts. We’ll z-score every pitch thrown over 100 times last year and sum up the scores. Let’s focus on starters — depth of arsenal matters more for them. And let’s report summed up z-scores as well as average ones per pitch. One tells us how good their collective pitches are, the other how even their arsenal is.

And one last word about weighting the two categories (grounders and whiffs). I correlated each pitch type whiff and grounder rates to overall ERA and SIERA estimates, and the resulting correlations are below.

Correlation Between Pitch Peripherals & Overall Estimators

	r ERA	r SIERA	r xFIP
Pitch swSTR%	0.2034	0.38728	0.32352
Pitch GB%	0.1314	0.11068	0.15158

r values reported above

There’s a decent amount of fluctuation depending on which estimator you’re using, but the relationship between pitch type swinging strike rates and those estimators looks to be generally about twice as strong as the relationship between pitch type ground ball rates and estimators. So, for the purposes of these scores, I doubled the z-score for swinging strike rate.

Below are 2015 Arsenal Scores along with ERA and strikeouts minus walks (12.3% was average or a starter last year).

Correlation Between Pitch Peripherals & Overall Estimators

Pitcher	Sum Arsenal Score	Average AS	Pitches	GS	2015 ERA	2015 K-BB
Carlos Carrasco	14.33	2.87	5	30	3.63	23.7%
Clayton Kershaw	10.87	3.62	3	33	2.13	29.1%
Jon Lester	9.74	2.43	4	32	3.34	19.3%
Jacob deGrom	8.59	1.72	5	30	2.54	22.2%
Noah Syndergaard	7.87	1.97	4	24	3.24	22.4%
Cole Hamels	7.74	1.94	4	32	3.65	17.4%
Jake Arrieta	7.22	1.44	5	33	1.77	21.6%
Francisco Liriano	6.86	1.72	4	31	3.38	17.5%
Chris Sale	6.49	2.16	3	31	3.41	27.2%
Garrett Richards	6.44	1.61	4	32	3.65	11.6%
Dallas Keuchel	6.04	1.51	4	33	2.48	18.1%
Chad Bettis	5.93	1.19	5	20	4.23	11.2%
Max Scherzer	5.91	1.48	4	33	2.79	26.9%
Carlos Martinez	5.61	1.40	4	29	3.01	16.0%
Gio Gonzalez	5.58	1.39	4	31	3.79	13.2%
Jose Fernandez	5.38	1.79	3	11	2.92	24.5%
Brandon McCarthy	5.24	5.24	1	4	5.87	26.6%
Corey Kluber	4.95	0.99	5	32	3.49	22.6%
Danny Salazar	4.45	0.89	5	30	3.45	18.8%
Stephen Strasburg	4.40	1.10	4	23	3.46	24.7%
Rich Hill	4.14	2.07	2	4	1.55	29.3%
Jaime Garcia	4.14	0.83	5	20	2.43	13.1%
Madison Bumgarner	4.08	1.02	4	32	2.93	22.4%
Joe Blanton	3.99	1.00	4	4	2.84	20.4%
Chris Archer	3.77	0.94	4	34	3.23	21.4%
Rubby de la Rosa	3.69	0.92	4	32	4.67	10.8%
Trevor Cahill	3.68	1.23	3	3	5.4	10.7%
Matt Harvey	3.63	0.73	5	29	2.71	20.0%
Matt Andriese	3.62	0.91	4	8	4.11	11.0%
Felix Hernandez	3.61	0.72	5	31	3.53	16.1%
Joe Ross	3.47	1.74	2	13	3.64	15.3%
Tyson Ross	3.44	1.15	3	33	3.26	15.6%
Raisel Iglesias	3.42	0.86	4	16	4.15	19.2%
Jarred Cosart	3.15	1.05	3	13	4.52	4.7%
Lance McCullers	3.07	0.77	4	22	3.22	16.5%
Michael Pineda	3.07	1.02	3	27	4.37	20.2%
Zack Greinke	3.04	0.61	5	32	1.66	19.0%
James Shields	2.77	0.69	4	33	3.91	15.7%
Zachary Davies	2.54	1.27	2	6	3.71	6.5%
Sonny Gray	2.49	0.50	5	31	2.73	13.2%
Yordano Ventura	2.41	0.60	4	28	4.08	14.1%
David Hale	2.36	0.59	4	12	6.09	11.9%
Patrick Corbin	2.36	0.79	3	16	3.6	17.1%
Nicholas Tropeano	2.34	0.78	3	7	3.82	17.4%
Drew Smyly	2.16	0.72	3	12	3.11	20.7%
Jerad Eickhoff	2.05	0.68	3	8	2.65	17.7%
Henry Owens	1.93	0.96	2	11	4.57	9.6%
Jimmy Nelson	1.92	0.48	4	30	4.11	11.0%
Gerrit Cole	1.88	0.63	3	32	2.6	19.0%
Erasmo Ramirez	1.84	0.37	5	27	3.75	12.9%
Shelby Miller	1.80	0.60	3	33	3.02	11.4%
Ariel Pena	1.78	0.89	2	5	4.28	10.8%
Travis Wood	1.76	0.88	2	9	3.84	18.9%
Chris Rusin	1.73	0.43	4	22	5.33	7.6%
Logan Verrett	1.69	0.56	3	4	3.59	12.6%
Kevin Gausman	1.66	0.55	3	17	4.25	15.7%
David Price	1.61	0.40	4	32	2.45	20.1%
Mike Fiers	1.53	0.51	3	30	3.69	15.2%
Scott Feldman	1.52	0.51	3	18	3.9	7.5%
Archie Bradley	1.51	0.75	2	8	5.8	0.6%
Chris Heston	1.39	0.46	3	31	3.95	10.3%
Marcus Stroman	1.34	1.34	1	4	1.67	11.7%
Luis Severino	1.32	0.44	3	11	2.89	13.3%
Brandon Finnegan	1.32	0.66	2	4	3.56	12.2%
Mat Latos	1.30	0.26	5	21	4.95	13.8%
Aaron Sanchez	1.25	0.42	3	11	3.22	4.5%
Michael Wacha	1.18	0.39	3	30	3.38	12.5%
Bud Norris	1.15	0.38	3	11	6.72	10.6%
Trevor May	1.12	0.28	4	16	4	17.1%
Hisashi Iwakuma	1.11	0.22	5	20	3.54	17.4%
Scott Copeland	1.08	1.08	1	3	6.46	5.8%
Steven Matz	1.02	0.51	2	6	2.27	16.1%
Dillon Gee	0.98	0.49	2	7	5.9	7.7%
James Paxton	0.94	0.31	3	13	3.9	9.1%
Clayton Richard	0.92	0.92	1	3	3.83	8.3%
Josh Tomlin	0.90	0.45	2	10	3.02	19.5%
Matt Moore	0.90	0.30	3	12	5.43	8.3%
Drew Pomeranz	0.78	0.26	3	9	3.66	14.3%
Severino Gonzalez	0.65	0.65	1	7	7.92	14.7%
Jeff Locke	0.63	0.21	3	30	4.49	9.4%
Ryan Weber	0.55	0.55	1	5	4.76	11.9%
Clay Buchholz	0.40	0.10	4	18	3.26	17.9%
Mike Bolsinger	0.28	0.09	3	21	3.62	11.4%
Chris Capuano	0.19	0.06	3	4	7.97	8.2%
Ian Kennedy	0.18	0.05	4	30	4.28	17.1%
Taylor Jungmann	0.12	0.03	4	21	3.77	12.0%
Keyvius Sampson	0.11	0.03	4	12	6.54	6.4%
Felix Doubront	0.08	0.02	4	12	5.5	9.2%
A.J. Burnett	-0.09	-0.02	4	26	3.18	13.5%
Vincent Velasquez	-0.11	-0.06	2	7	4.37	16.0%
Jonathan Gray	-0.14	-0.05	3	9	5.53	14.1%
Carlos Rodon	-0.14	-0.04	4	23	3.75	11.2%
Robbie Erlin	-0.22	-0.22	1	3	4.76	12.3%
Johnny Cueto	-0.24	-0.06	4	32	3.44	15.0%
Collin McHugh	-0.32	-0.08	4	32	3.89	13.7%
Adam Conley	-0.39	-0.13	3	11	3.76	13.5%
Kris Medlen	-0.40	-0.10	4	8	4.01	9.1%
Cody Anderson	-0.47	-0.23	2	15	3.05	5.5%
Taijuan Walker	-0.49	-0.16	3	29	4.56	16.6%
Daniel Norris	-0.55	-0.14	4	13	3.75	10.4%
Michael Lorenzen	-0.59	-0.12	5	21	5.4	5.1%
T.J. House	-0.59	-0.59	1	4	13.15	-6.9%
Mike Wright	-0.69	-0.35	2	9	6.04	3.9%
Tyler Wilson	-0.76	-0.38	2	5	3.5	1.3%
Randy Wolf	-0.78	-0.39	2	7	6.23	8.1%
Jake Odorizzi	-0.80	-0.27	3	28	3.35	14.9%
Chad Billingsley	-0.82	-0.41	2	7	5.84	4.2%
Aaron Nola	-0.83	-0.21	4	13	3.59	15.4%
Jesse Chavez	-0.83	-0.21	4	26	4.18	13.1%
Kyle Ryan	-0.85	-0.43	2	6	4.47	4.2%
Jose Quintana	-0.91	-0.23	4	32	3.36	15.4%
Matt Garza	-0.92	-0.23	4	25	5.63	7.1%
Allen Webster	-0.95	-0.32	3	5	5.81	-2.1%
Tsuyoshi Wada	-0.98	-0.98	1	7	3.62	14.7%
Michael Montgomery	-1.02	-0.34	3	16	4.6	6.8%
Jeff Samardzija	-1.10	-0.28	4	32	4.96	12.5%
Tanner Roark	-1.11	-0.28	4	12	4.38	9.4%
Jeremy Hellickson	-1.13	-0.28	4	27	4.62	12.3%
Jorge de la Rosa	-1.16	-0.39	3	26	4.17	10.9%
Carlos Frias	-1.16	-0.58	2	13	4.06	5.1%
Yohan Flande	-1.26	-0.42	3	10	4.74	6.1%
Drew Hutchison	-1.27	-0.42	3	28	5.57	12.8%
Nate Karns	-1.35	-0.45	3	26	3.67	14.3%
Steven Wright	-1.36	-0.68	2	9	4.09	8.1%
Jhoulys Chacin	-1.39	-0.70	2	4	3.38	9.9%
Jason Vargas	-1.41	-0.70	2	9	3.98	8.2%
CC Sabathia	-1.42	-0.35	4	29	4.73	12.0%
Jordan Zimmermann	-1.42	-0.47	3	33	3.66	15.0%
Josh Collmenter	-1.51	-1.51	1	12	3.79	7.8%
Edinson Volquez	-1.55	-0.39	4	33	3.55	9.8%
Roenis Elias	-1.58	-0.40	4	20	4.14	10.8%
Chase Whitley	-1.64	-0.82	2	4	4.19	13.1%
Alex Wood	-1.79	-0.45	4	32	3.84	10.0%
R.A. Dickey	-1.89	-1.89	1	33	3.91	7.4%
Brandon Morrow	-1.89	-0.94	2	5	2.73	12.7%
Jason Marquis	-1.94	-0.65	3	9	6.46	10.7%
Kyle Gibson	-1.97	-0.39	5	32	3.84	9.7%
Tommy Milone	-1.98	-0.66	3	23	3.92	10.1%
Chi Chi Gonzalez	-1.98	-0.66	3	10	3.9	-0.7%
Jose Urena	-1.99	-0.66	3	9	5.25	1.1%
Jesse Hahn	-2.00	-0.50	4	16	3.35	9.6%
Hector Noesi	-2.06	-1.03	2	5	6.89	3.3%
John Lamb	-2.09	-1.04	2	10	5.8	17.7%
Brett Anderson	-2.10	-0.42	5	31	3.69	9.3%
Miguel Gonzalez	-2.14	-0.43	5	26	4.91	9.3%
Dan Straily	-2.18	-2.18	1	3	5.4	7.9%
Lance Lynn	-2.27	-0.57	4	31	3.03	13.2%
John Lackey	-2.30	-0.77	3	33	2.77	13.6%
Tyler Duffey	-2.35	-0.78	3	10	3.1	13.6%
Jerome Williams	-2.43	-0.81	3	21	5.8	7.2%

Arsenal Score: Sum of (2*swSTR z-score+1*gb z-score)
Average AS: AS divided by number of qualifying pitch types that pitcher throws

The list is full of studs, and with all the love we have for Carrasco here at RotoGraphs, it’s not surprising to see him on top of the grouping. It’s also nice to have Clayton Kershaw at the top of the list, at least for our sense of well being.

The first name that leaps out is Chad Bettis. Last year, his changeup, slider, and curve were all well above-average by whiff rates, and the change has excellent drop both relative to his fastball (five inches more) and relative to the average change (three inches more). The slider is relatively fast, at 87, and the curve gives him a third look and speed. His fastball isn’t impressive, but it has a little natural cut to it, and it looks like we can believe his mini-breakout despite average strikeout and walk numbers.

Brandon McCarthy‘s numbers were changed by his small sample entry, and Rich Hill’s as well. Both had dominant pitches — McCarthy’s super-charged four-seamer, and Hill’s four-seamer as set up by his crazy curve — but without more data we can’t give them they same stamp, really.

Danny Salazar, Raisel Iglesias, Lance McCullers, Yordano Ventura — do we need this to pump them up more? They’re established young sleeper types. But it is nice to see that their pitches are, you know, good.

How about a second group of guys that we should look closer at? Rubby de la Rosa, Joe Ross, Jarred Cosart, and Henry Owens? We’ve done some writing about de la Rosa’s new harder slider and how that might work with his changeup, we all know how nice the Ross family slider hums, and Owens had some pedigree to go with a nice rising fastball. Maybe Owens deserves more love than his ERA and strikeout rates suggest he should. Cosart? Command is the bugaboo of course.

Do we give more love to a K-BB star if they are high on this list? Jerad Eickhoff and Nicholas Tropeano have divided analysts so far, mostly because their fastballs aren’t great. And that might be a weakness in this analysis — we don’t weight the fastball more, even though they are more important to outcomes. But because of other factors (park for Tropeano and league for Eickhoff) maybe home run issues off of the fastball are less of a concern here. Eickhoff has the role, so Tropeano is a lesser sleeper, at least until he has a confirmed role, but both of these guys rate as mixed league sleepers to me.

The list is fun, but it’s not the end of the line. By adding this to KPU-BB (updated so that it’s PU/TBF), we can have a non-traditional look at peripherals that may become more meaningful in smaller samples. That’ll help with guys like Eickhoff and Luis Severino, who didn’t give us a ton of major league innings last season. Once I group this data, I’ll be able to put together my pitching ranks.