Masahiro Tanaka and Homers and Strikeouts

The Yankees have been a beacon of mediocrity this year, currently sitting under .500 and in fourth place in the resurgent AL East. Pitching is often a soft spot for the Yankees, as Yankee Stadium routinely ranks in the top half of the league in terms of worst parks for pitchers, according to park factors on FanGraphs. The short porch in right field is especially troublesome for hurlers. For this reason, park factors on FanGraphs have listed Yankee Stadium (tied with others) as the easiest park for a lefty to hit a homer from 2013-2015. Thus, there are bound to be some interesting trends among their starters. One such starter is the always entertaining Masahiro Tanaka. Let’s explore!

Tanaka struggled mightily with the longball during his first two seasons with the Yankees, posting a 1.24 HR/9 ratio from 2014-2015, which would have been good (or bad) enough for the eighth-highest among starters, had he qualified. That includes a ridiculous 1.46 HR/9 from last year, which would have ranked sixth (a few spots behind teammate CC Sabathia, who ranked third with 1.51 HR/9). At the same time, that high HR/9 may have been because Tanaka was victimized by a 15.7% HR/FB ratio during those two seasons. Since Tanaka is a righty (opposing teams are more likely to play lefties against him) who pitches half of his games at Yankee Stadium (lefty heaven), his HR/FB ratio is bound to be high, but not that high. Thus, it’s understandable that his HR/FB ratio decreased to a more normal 9.5% this year. It will probably be higher than that in the future, but this is just the ebb and flow of things: sometimes stats are higher than they should be, and sometimes they are lower.

Tanaka actually allowed a palatable 0.99 HR/9 in his first season with the Yanks, despite a 14.0% HR/FB ratio. His groundball rate remained virtually the same from that first season to the second, but one thing that made his home-run total lower in his first season as opposed to the second (other than a slight uptick in HR/FB) was a 9.3 K/9. When you allow fewer balls in play, you will allow fewer homers. However, in Tanaka’s second season, that number sunk to 8.1 K/9, a substantial drop. It has dropped even further this season, considerably below league average now at 7.1 K/9. What has brought about this dip in Ks? Changes in velocity often coincide with changes in K-rate:

Year	Fourseam	Sinker	Change	Slider	Curve	Cutter	Split
2014	92.74	91.44	87.49	83.97	74.41	89.26	87.27
2015	92.76	91.69	0.00	84.42	77.08	89.73	88.04
2016	92.63	90.63	0.00	84.86	75.91	88.53	86.93

Interesting. His velocity has remained quite stable throughout his time with the Yankees (if you look year to year). Let’s look elsewhere. Another determining factor for K-rate is movement. Here is Tanaka’s horizontal movement over the years.

Year	Fourseam	Sinker	Change	Slider	Curve	Cutter	Split
2014	-4.66	-8.17	-7.81	3.01	5.26	-0.99	-4.83
2015	-5.79	-8.72	0.00	1.54	4.20	-1.85	-6.45
2016	-5.80	-8.26	0.00	1.08	4.60	-2.08	-6.67

His slider, cutter, and curve have lost a bit of that typical movement away from righties, but at the same time, the four-seam and split have improved their arm-side run, inside to righties. The sinker has pretty much held steady. How about vertical movement?

Year	Fourseam	Sinker	Change	Slider	Curve	Cutter	Split
2014	9.37	5.52	4.33	1.38	-6.34	5.50	1.63
2015	9.56	5.98	0.00	2.03	-4.18	6.45	2.21
2016	9.94	5.74	0.00	3.47	-4.58	6.53	2.74

All of his pitches are dropping less/rising more, which is good for the four-seamer and cutter, but not so good for everything else. There are some good and some bad movement trends, but nothing that I would think would completely evaporate Tanaka’s strikeouts. There has to be something else. Has Tanaka’s whiff rate changed at all?

Year	Fourseam	Sinker	Change	Slider	Curve	Cutter	Split
2014	5.16	5.91	0.00	16.39	5.26	13.82	29.13
2015	5.66	4.02	0.00	16.70	4.05	8.63	20.62
2016	6.00	4.51	0.00	18.85	5.13	12.39	17.11

Indeed it has. The splitter has seen a sharp drop in swinging strike rate. Why is this happening? Did Tanaka change something? Let’s see if his pitch mix has any answers.

Year	Fourseam	Sinker	Cutter	Curve	Slider	Change	Split
2014	21.34	19.49	6.16	5.71	21.39	0.10	25.80
2015	18.64	13.62	10.75	7.30	22.23	0.00	27.41
2016	3.07	34.01	6.94	4.79	25.72	0.00	25.48

Woah! Tanaka has completely scrapped his four-seamer in favor of his sinker. Everything else has remained relatively stable. Here’s where we come full circle — back to the homers. I have a feeling that his reasoning for this change was that he wanted to improve his groundball rate in order to allow fewer home runs. Sure, the groundball rate has improved a little (up 3.4% in since last year), but this pitch swap seems to be the biggest reason I can think of for the sharp decrease in swinging-strike rate for Tanaka’s splitter. My theory is that his four-seamer, a relatively straight, hard pitch with a bit of rise, can help set up the splitter better than the sinker. The sinker and splitter are almost the same pitch; the split has a bit more drop, a bit more run, and is a bit slower. The velocity difference and movement difference between the splitter and four-seamer is much more drastic than those differences between the sinker and the split.

So, Tanaka seems to have traded some strikeouts for a few more groundballs/fewer homers. I’m not sure I like this change; his HR/FB rate was bound to normalize anyway. However, one thing I certainly like from Tanaka this year is that he has stayed off the DL. An asterisk has been over his name on draft day since the UCL injury a couple of summers ago. Despite staying off of the DL this year, people have been pointing to his better record on extra rest as a sign of fatigue. In 10 starts on extra rest this year, Tanaka has a 1.72 ERA, versus a 5.28 ERA in seven starts on regular rest. However, this has never been a noticeable split before this year, and it’s also worth noting that seven of those 10 starts have come away from Yankee Stadium, which I have deemed a bad park for Tanaka to pitch in.

Graphs and tables are from Brooks Baseball.