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Breaking down Yankees starter Masahiro Tanaka’s strong start to 2019

A deep dive into Tanaka’s first three starts reveals an encouraging trend.

MLB: New York Yankees at Houston Astros Thomas B. Shea-USA TODAY Sports

Masahiro Tanaka has been one of the Yankees’ brightest spots in what has otherwise been a rather frustrating start to the season. Tanaka’s 1-0 record to date isn’t exactly eye-popping, but given the way he’s pitched, he’d be 3-0 if not for poor offensive showings and relievers not relieving.

To wit: in 3 starts and 18.1 innings so far, Tanaka’s ERA stands at a cool 1.47, his FIP a very strong 2.48. His strikeout total of 15 is rather modest in and of itself, but it’s plenty impressive when juxtaposed with his walk total of just two. In addition, Tanaka has only allowed one homer so far this year, a moonshot off the bat of Jose Altuve in his most recent start against the Astros. Imagine if Tanaka kept limiting homers at this pace - coupled with his stellar strikeout and walk numbers, he’d be a legitimate Cy Young candidate.

Of course, it’s important not to lose perspective. Three starts does not a season make, especially when two of them came against two of the weakest teams in the league (namely, the Orioles and Tigers). However, Tanaka has show underlying trends in these three starts that suggest he might have found a way to limit the long ball.

Put simply, Tanaka has become a groundball machine this year. His groundball rate this year stands at a robust 57.4%, up more than 10 points from last year and 9.4 points above his career average. It’s not like one abnormal start is skewing his 2019 totals, either. Tanaka has generated a 55% groundball rate or better in each of his starts this year.

Yes, it’s just three starts, but this uptick in Tanaka’s groundball rate is still a notable development. The last time Tanaka managed such a feat in three consecutive starts was between August 27th and September 8th of 2017. As the graph below shows, Tanaka’s 15-game rolling groundball rate is now at a higher level than it ever was all throughout 2018.

Masahiro Tanaka 15-game rolling GB%, 2017-2019

If Tanaka is able to keep generating wormkillers at a similar pace, his home run problem would be all but solved, and his overall performance level would soar. Fortunately for the Yankees, and for us fans, this uptick in groundball rate appears to be the result of a subtle adjustment on Tanaka’s part.

The adjustment is straightforward; Tanaka has changed the location of his splitter. Rather than burying it in the dirt, as was his previous modus operandi, this year he’s throwing it for strikes more often, locating it in the bottom half of the strike zone. This subtle shift is shown clearly between the two heatmaps below, both showing how Tanaka has located his splitter; the first from 2014-2018, and the second showing data from 2019.

Tanaka splitter heatmap, 2014-2018
Tanaka splitter heatmap, 2019

This change has resulted in Tanaka’s splitter generating fewer whiffs than in 2018, but also substantially more groundballs.

Tanaka splitter whiff rate, 2018-19
Tanaka splitter ground ball rate, 2018-19

The change makes sense, if you think about it. Tanaka has been in the league for quite some time now, and batters have progressively gotten better at laying off his splitter when it’s buried. The numbers attest to this; Tanaka’s splitter, while retaining essentially the same movement, has generated lower run values from 2017 onwards.

By locating his splitter around the lower edge zone rather than below it, Tanaka can coax more batters to swing at it. They would make more contact, sure, but the nature of that contact would likely be weak provided the pitch is breaking properly - it’s designed to get under over-eager bats. And while this new strategy does make hanging a splitter that much more punishing, Tanaka has mitigated this risk by reining in his usage a bit (30.2% last year to 27.5% this year), opting to go to his slider a little bit more often (32.4% to 34.8%) to keep hitters off balance.

Yankee fans have long known Tanaka to be a perfectionist whose dedication to his craft is unparalleled. This adjustment is the latest proof of that dedication, and it’s generated stellar results so far. With Luis Severino’s setback, the Yankees desperately need stability in the rotation. Look for the ever-changing Tanaka to be the anchor of the group.