More Fun with Pitch Arsenal Scores

On Tuesday, I examined the case for Erasmo Ramirez and tried to find any glimpse of hope that he might turn into a useful major league pitcher. I used a new metric called Arsenal Score to find specific pitch-type data. It turns out, Erasmo has two plus pitches -- his fastball and his changeup -- that show he may yet be of some use. But his breaking balls are terrible and are probably the reason his results haven't matched his pitch-type peripherals.

Here's what I wrote about Arsenal Score from Tuesday's post:

Eno Sarris and Daniel Schwartz have been developing a Pitch Arsenal score for pitchers to determine which pitchers have the best pitch arsenal to call on. If a pitcher is able to get batters to swing and miss and induce grounders with a pitch, the outcomes should be pretty favorable for the pitcher when they use that pitch. You can read about the methodology here and here. In short, Sarris and Schwartz have calculated z-scores for whiff per swing rate and the ground ball to fly ball ratio for every pitch that was thrown over 100 times by starters who threw at least 60 innings in 2014 (221 pitchers under this criteria). The combined weighted z-scores give a pitch score and the pitch scores are summed to give an Arsenal Score.

I really liked the type of analysis Arsenal Score allowed me to perform. It's more granular than some of the other pitch-type metrics we have available elsewhere. FanGraphs has weighted run values for individual pitch types that give us some clue as to which pitches perform the best. But these run values are dependent on results that may or may not correlate well from year to year. Things like home run rate and batting average on balls in play require thousands of data points to become reliably predictive for pitchers. Other stats like strikeout rate, walk rate, and ground ball rate take very few data points to become reliably predictive.

Weighted run values for individual pitch types are certainly helpful and they have their place. I like Arsenal Score for its simplicity and its reliance on two metrics that stabilize fairly quickly -- whiff rate and ground ball rate. With all this in mind, I wanted to take a look at the rest of the Mariners rotation through the lens of their Arsenal Score.

Felix Hernandez

Pitch	Velocity	Frequency	Whiff/Swing	GB/FB	Pitch Score
Fastball	93.68	12.9%	14.8%	1.92	-0.03
Sinker	93.03	31.1%	12.0%	2.10	-0.10
Change	89.96	31.4%	39.0%	4.75	0.97
Slider	85.22	8.2%	41.5%	7.50	1.77
Curve	81.01	16.2%	40.6%	6.68	1.34
					3.95

It's no secret that Felix is one of the best pitchers in the league and his Arsenal Score backs that notion up. He's almost four standard deviations above average and three of his pitches are plus pitches. I'm surprised that Felix's sinker (or two-seam fastball depending on the classification system) doesn't get many ground balls compared to league average. He makes up for that shortcoming with his ability to generate a ridiculous amount of grounders off his off-speed pitches.

It's interesting to see how different a pitcher Felix has become since his debut. Young Felix used his fastball and his slider to generate a high amount of swinging strikes. As he's evolved, his changeup has developed into a dominant pitch and he's become less reliant on his slider. His curveball hasn't ever stopped being a weapon as it's one of the best curveballs in the majors.

Hisashi Iwakuma

Pitch	Velocity	Frequency	Whiff/Swing	GB/FB	Pitch Score
Fastball	90.23	13.7%	25.8%	0.61	1.12
Sinker	89.26	35.0%	8.4%	3.34	-0.52
Slider	81.05	19.4%	25.3%	1.56	-0.68
Curve	73.36	3.2%	6.3%	1.17
Cutter	87.42	1.3%	30.0%	0.00
Splitter	85.00	27.3%	27.9%	7.20	0.20
					0.12

Hisashi Iwakuma's Arsenal Score was the most surprising of all. He just does not generate that many whiffs with his off-speed pitches. Yet, despite the lack of whiffs, Iwakuma has been able to run a strikeout rate above 20%. That high strikeout rate seems to stem from his ability to generate called strikes. I don't have league average called strike rates for individual pitch types but Iwakuma ran a 17.5% called strike rate on his curveball last year and a 27.84% called strike rate on his sinker. It seems like Arsenal Score overlooks pitchers who are able to generate a high amount of called strikes with their pitches like Hisashi Iwakuma.

James Paxton

Pitch	Velocity	Frequency	Whiff/Swing	GB/FB	Pitch Score
Fastball	95.48	66.4%	10.5%	3.35	-0.33
Change	87.29	8.9%	43.9%	4.00	1.22
Curve	82.50	18.4%	32.6%	10.00	1.27
Cutter	90.53	6.1%	25.0%	0.00
					2.16

Arsenal Score loves James Paxton's pitch repertoire. His curveball and changeup are more than a standard deviation above average. Paxton is able to generate a huge amount of whiffs with is changeup and his curveball forces batters to pound the ball into the ground. In fact, across the board, Paxton's pitches run above average ground ball rates leading to the 10^th highest ground ball rate among starters with at least 70 innings pitched last year.

Paxton's fastball seems to be a victim of Arsenal Score's limitations. He generated a 20.09% called strike rate with his fastball last year. Even if his fastball wasn't a weapon, he'd probably be able to get by on his curveball and changeup alone anyway.

J.A. Happ

Fastball	93.34	52.8%	17.8%	0.81	0.15
Sinker	93	19.1%	11.4%	4.36	0.13
Change	86.11	9.5%	13.2%	1	-1.44
Curve	78.3	12.2%	23.5%	2.21	-0.43
Cutter	84.14	6.4%	26.2%	1.57	0.40
					-1.19

The newest member of the Mariners rotation doesn't grade out very well according to Arsenal Score. J.A. Happ's fastballs are all above average, which could be a result of his increased velocity he showed last year. However, his off-speed pitches are decidedly below average. His changeup is one of the worst in the majors.

Roenis Elias

Pitch	Velocity	Frequency	Whiff/Swing	GB/FB	Pitch Score
Fastball	92.88	43.0%	13.4%	1.45	-0.28
Sinker	92.76	9.5%	9.2%	3.71	-0.33
Change	86.5	24.1%	38.0%	2.92	0.68
Curve	79.82	23.2%	35.8%	3.83	0.59
					0.66

Roenis Elias throws two above average pitches. We knew about his curveball, as that's his go to strikeout pitch, but his changeup also grades out well via Arsenal Score. Elias' ground ball rate is just above league average and that's reflected in his granular pitch ground ball rates.

Taijuan Walker

Pitch	Velocity	Frequency	Whiff/Swing	GB/FB	Pitch Score
Fastball	95.26	58.7%	19.7%	2.57	0.68
Curve	74.85	13.6%	12.5%	2
Cutter	91.81	8.6%	31.0%	1.5
Splitter	88.56	18.5%	34.2%	3	0.03
					0.71

In his limited time in the majors, Taijuan Walker has shown that his fastball and his cutter are real weapons that are able to generate whiffs at an impressive rate. His off-speed pitches could use some real work however. His curveball just does not generate any whiffs and is probably the one pitch that he needs to work on before he's ready to claim a spot in the major league rotation.

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I'm thinking about including these Arsenal Score graphs in my series previews once the season starts. Is this helpful data for you? What could be improved before I start building these graphs in earnest? What do you think?