I had to dig through and revamp my code for generating the pitch grades that form the basis for those aggressively multi-colored charts you see in the series previews. While doing so, I SQL stumbled into noticing Hisashi Iwakuma's pitch breakdowns as a starter versus as a reliever and one pitch, used while in the rotation, caught my notice.
Up front I will say that this is all based on pitch F/X's classification system, which isn't perfect. It's good enough for my tastes, but if someone wants to do a thorough breakdown of Iwakuma's pitch types by hand, by all means. The data is available out there.
The particular pitch in question is Iwakuma's curve ball. No, it's not. It's his sinker. Of course it's his sinker, it's right there in the headline. I assume you read the headlines, but given how often people fail to read the byline, perhaps I am overoptimistic in that regard. Anyways, as a starter, Iwakuma has so far thrown 86 sinkers. That is not many, no sirree, so don't go traipsing 'round the ol' internet blaring your horn about Iwakuma's sinker data. There ain't much.
What I noticed from what is there though was that 41 times a hitter was swung at Iwakuma's sinker, and 41 times the hitter connected, a 100% contact rate. 21 have been fouled off, 12 put in play on the ground (eight outs, three singles and a double) and eight times in the air (five outs, a single, a double and a home run). No other pitcher in the last two years has thrown a pitch as often as Iwakuma has that sinker without getting at least one swing and miss. There is little meaning in Iwakuma's sinker numbers given the small sample, but while I was looking at that, I decided to peek at the reverse as well.
On the complete other end of the spectrum is, or rather more likely was, Sergio Santos' slider. Santos, now on the shelf after shoulder surgery, had his slider swung at 195 times over the past 730 days. Of those 195 swings, 123 of the missed. The contact rate on Santos' slider was 37%. Honorable mention goes out to Ryan Madson's changeup, which has the league's highest overall swinging strike rate, which differs from contact rate in the denominator used, and has long been a devastating weapon of his.
Iwakuma does have some good pitches as well. His split-fingered fastball compares favorably to average. And hey, at least Iwakuma takes a really long time to throw!