MLB: ALCS-Houston Astros at New York Yankees

Statcast Year in Review: Masahiro Tanaka

Within three days of the end of the World Series, Masahiro Tanaka will have to decided whether or not to opt-out of the final three years and $66 million of his contract. His is one of the more interesting opt-out cases to come up in recent years. Will he opt-out? Should the Yankees re-sign him if he does? Let’s start by reviewing the season.

Tanaka’s top line statistics on the season:

  • 30 starts
  • 178 1/3 innings
  • 9.8 K/9, 2.1 BB/9
  • 4.74 ERA, 4.31 FIP, 3.66 DRA
  • 3.8 WARP

Already, a blurry picture emerges. A pitcher with a 3.66 DRA is pretty good, and definitely worth three years, $66 million. A pitcher with a 4.74 ERA, even in Yankee Stadium, is below average.

Of course, Tanaka got better as the season went on. His ERA was 3.77 after the All Star break, and Tanaka was dominant in the playoffs. Was Tanaka just unlucky in the first half, or is there a bigger problem?

Statcast provides us the perfect tool to answer this question. On every ball in play, Statcast records an exit velocity and launch angle. These two variables can be combined to produce very reliable predictions of the run value outcome of the batted ball. Combined with strikeout and walk data, Statcast produces a statistics called xwOBA, or expected wOBA. A full explainer is here.

How did Tanaka perform according to xwOBA this season? Below is a 3-game rolling average for the regular season:


The data tell a very clear story. At the beginning of the season, Tanaka pitched like an above-average (although only slightly-so) AL pitcher. Something went horribly wrong in May, and he turned the average batter he faced into peak Aaron Judge. He corrected something in June, then performed consistently like his 3.77 second-half ERA for the rest of the season. For what it’s worth, PECOTA projects almost exactly the same ERA for Tanaka.

I don’t look at these data and see an ace. I see a pitcher who, at his best, is pretty good. He also has enormous downside. We’ve known about Tanaka’s downside for awhile now. When he’s off, he allows home runs. A lot of home runs. It makes sense that he’ll have rough patches.

If I were Masahiro Tanaka’s agent, I’d think twice about opting out. There might be a few teams willing to overpay for his amazing playoff performance, but it’s not clear that he’s worth a $100+ million contract. If he does opt out, I hope Brian Cashman passes.

Photo Credit: Robert Deutsch-USA TODAY Sports

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