Tanaka’s Falling Strikeout Rate

There’s no denying that Masahiro Tanaka had a brilliant season in 2016. For the first time in his three-year career, he had a legitimate shot at the Cy Young Award and ended up finishing seventh in the balloting. He tied his career high in ERA- at 72 and was close to his career high FIP- of 78 with a mark of 80 this year; he put up a career high ground ball rate while notching new career lows in infield fly ball percentage and home run/fly ball percentage. The only thing he didn’t do as well as he’d done previously is strike batters out.

Continuing a trend, Tanka’s K/9 dipped again this year, falling to 7.44 from 8.12, which was down from 9.31 in 2014. His K% shows a similar downturn, going from 26 in 2014 to 22.8 in 2015 and 20.5 in 2016. 20.5 K% is still good, especially considering he’s never posted a BB% above 4.5 (this year’s mark). And given the change in approach that Mike described here, a drop in strikeout numbers wouldn’t be unexpected. Still, it’s worth taking a look to see what’s behind the dip in whiffs because punchouts are fun and the most efficient way to get a batter out.

Let’s start with the out-pitch, the one whose reputation came in tow when Tanaka arrived in MLB, the splitter. In 2014, he generated a 46.01 whiff/swing rate on the pitch. It dropped to 33.33 in 2015, then to 30.00 in 2016. As a percentage of his strikeouts, the splitter has gone from being about half of them (2014) to about a third of them or a little more (2015-16). Of course, when your groundball/balls-in-play percentage is in the mid to high sixties with a pitch, the declining strikeout rate is something you can live with. Tanaka’s slider tells a similar story. The whiff/swing rate on his slider has gone from 39.55 to 34.38 to 33.16. The GB/BIP rate has gone from 31.37 to 39.00 to 40.74.

If we take a look at the splitter and where Tanaka likes to throw it, we get a good idea of why whiffs and grounders happen. The bottom drops out of the splitter and the batter either swings over it or beats it into the ground. The conclusion drawn before–fewer strikeouts, more grounders–is fleshed out here as well. Take a look at the whiff/swing rate on Tanaka’s three most popular spillter locations in 2014, 2015, and 2016; there’s a general downward trend, suggesting that hitters are making more contact with those pitches, even if they’re not doing a lot with them. His slider has shown a similar trend, gathering more grounders in the lower part of the zone as the years have gone on.

We tend to take a drop in strikeout rate as a cause for alarm among pitchers and I’m generally inclined to agree with that quick assessment. However, while it’s something to watch with our beloved, underrated TANAK, I’m not overly worried. He showed this year that he can be incredibly successful without having to get too many strikeouts and, frankly, this is a microcosm of him as a pitcher. Each game, Tanaka seems to bring a new strategy, a new approach to the mound and that’s been true on the broad scale of his three year career. As a pitcher who seems to reinvent himself every start, he’s capable of displaying greatness in myriad ways, strikeouts or not.