Hisashi Iwakuma's Logic-Defying Fastball

Who would have thought that arguably the leading candidate for the 2013 AL Cy Young Award would be a Seattle Mariner not named Felix Hernandez? As good as King Felix has been, rotation mate Hisashi Iwakuma has been even better. In his second season stateside, Iwakuma ranks second among qualified major league starters in ERA+ (204) and strikeout-to-walk ratio (6.21).

The 32-year-old righty has emerged as an ace in part due to dramatic improvement with his fastball. Hitters are slugging just .362 against the pitch this season, compared to .595 in 2012. Iwakuma's success with his fastball flies in the face of baseball logic -- he's throwing it slower and putting it over the plate more often, yet he's getting swings and misses like a flame-thrower

Iwakuma didn't throw hard during his rookie season, with an average fastball velocity (90.3 MPH) that was one tick below the MLB average for right-handed starters (91.3 MPH). This year, he's lost some of his already modest zip, averaging 89.5 MPH on the radar gun. At the same time, Iwakuma has increased his percentage of fastballs thrown within the strike zone from about 58% to 62%. No starter outside of knuckleballer R.A. Dickey has pumped more fastballs over the plate this season.

As you might imagine, slow fastballs get fewer swings and misses (11.8% for sub-90 MPH gas) than higher-velocity heaters (15.6% for 90+ MPH fastballs). And fastballs thrown over the plate get dramatically fewer whiffs (12.1%) than out-of-zone fastballs (22.1%). Iwakuma was already a soft-tosser who filled up the strike zone in 2012, and those tendencies only became more pronounced in 2013. Therefore, his fastball miss rate should drop, right? Wrong.

Iwakuma's fastball contact rate, 2012

Iwakuma's fastball contact rate, 2013

In 2012, Iwakuma got swings and misses with his fastball 14.5% of the time. This year, while throwing more soft strikes, he's getting whiffs at a 22.5% clip. To put that into context, Yu Darvish (27% fastball miss rate), Shelby Miller (25.5%) and Matt Harvey (24.2%) are the only starters to miss lumber at a higher rate. Darvish (92.9 MPH average fastball velocity) Miller (93.4 MPH) and Harvey (95 MPH) all bring the heat. One of these things is not like the other. Iwakuma's fastball remains a mystery, to hitters and analysts alike.