Tanaka's fastballs are failing him this season

Masahiro Tanaka lived up to just about all the hype he could in his first season in pinstripes.  While he did tear his UCL, which has every Yankee fan on pins and needles every time he torques his elbow to unleash a wicked splitter, he still posted a 2.77 ERA, a 3.04 FIP and a terrific 9.31 K/9 ratio last season.  When healthy, he was everything we hoped he'd be when Brian Cashman backed up the Brinks truck to bring him to the Bronx.  This year, though, while he's remained relatively healthy, he hasn't been quite as dominant.  A 4.17 FIP and an 18.0 HR/FB% (one of the highest in the league) have shown that Tanaka is certainly mortal, and maybe closer to the number three starter Brian Cashman said he was all those months ago. What's behind his mild decline this year? Two fastball pitches that simply aren't missing bats, mainly because he has struggled to locate them.

Culprit #1: Tanaka's Sinker

Tanaka's biggest problem in 2015 has been his sinker.  While he's not throwing it nearly as much as he did in 2014 (when it was also a problem), this hasn't helped mitigate the fact that batters simply tee off against his sinker.  Tanaka's getting strikes on just 20% of his sinkers and whiffs on just 2.84% of them - but, for a pitch designed to induce weak contact (especially grounders), perhaps that's not a problem.  Wrong.  Tanaka's getting a lower ground ball percentage on his sinker than he did last year, and has been especially prone to the long ball with his sinker, as he's giving up a homer on 3.32% of them he throws (for reference, with his splitter - his best pitch - he only surrenders a homer on 0.27% of pitches).  He's also allowing a line drive on nearly 30% of sinkers that are put in play.  Batters are hitting .390 with an .848 slugging percentage against his sinker to go with a ridiculous .458 ISO, meaning when hurling this pitch, Tanaka basically turns opposing hitters into godlike monsters.  He did not have a great sinker last year, but it's gotten even worse this year.  Take a look for yourself:

Yeesh.  Some of his problem comes from him not getting his sinker down in the zone - he leaves a lot of them up in the middle of the plate.  You can see for yourself in the graph below, which covers his sinker locations over the past month:

Culprit #2: His Four-Seam Fastball

His four-seam fastball hasn't been a whole lot better.  This pitch proved problematic last year, and it is getting hit hard again this year.  Again, location has proven to be a big issue for Tanaka on this pitch:

It's never good to be have one of the most common locations for your fastball be right down the middle.  Here's another example of his location issues - take a look at where his four-seamer has found the plate over his last four starts (during which Tanaka has given up 12 runs and six homers):

As you can see, he's been leaving a lot of four-seamers in the heart of the plate recently, and these locations are representative of his entire season. Overall, opposing batters are hitting .312 with a .623 slugging percentage and a .312 ISO against his four-seamer. Batters are also hitting line drives on 30% of these fastballs that they put in play. Combined with his sinker, opposing lineups are loading up on these pitches and putting a serious hurting on them.  Since they combine to form over a third of the pitches Tanaka throws, that's a serious problem (and help set up his slider and splitter), that's a serious problem.

While his slider and split-finger fastball remain excellent weapons, it's hard to be an elite pitcher without being able to throw a few fastballs every now and then for a strike.  Obviously Tanaka hasn't had a bad year by any means, but his fastball struggles could prevent him from being a true ace.  It also doesn't help that his curve also gets drilled, but at least he hardly throws that (I wonder why).  With the Yankees rotation in need of stability, this is the worst time of year for Tanaka to start slipping in his performance.  Hopefully he can improve his sinker and four seamer a bit, which will in turn probably make his split and slider more effective, and hopefully give the Yankees the ace (or at least dominant number two starter) they will need to make any noise in the playoffs, or perhaps to make the playoffs at all.