Don’t Fall Behind Hisashi Iwakuma

There aren’t many reasons to watch the Seattle Mariners. For several years now there was a singular reason to do so and it had something to do with a guy who goes by “King.” But in 2013, there’s an encore for every Felix Hernandez gem and his name is Hisashi Iwakuma.

Seattle is the kind of media market that ensures players fly under the radar (see Martinez, Edgar). So there are probably plenty of you that look up from your spreadsheets and see a 7-1 record with a 1.79 ERA and 0.82 WHIP and wonder how you could have completely forgotten about this guy.

Nevertheless, here we are in mid June and Iwakuma has the second best ERA in baseball (among qualified starters) and damn near the same strikeout rate as Clayton Kershaw. While it seems extremely unlikely that Iwakuma can keep this up, the question on my mind is whether he can replicate any sort of approximation of his first 14 starts.

There are two quick things to keep tucked away in the back of your pretty little heads when pondering Iwakuma’s future. One, he’s had a series of shoulder issues in his career, although he’s been relatively healthy going on two seasons now. This is ostensibly why the club used him out of the pen to start 2012 and also why he’s only averaging 93 pitches per start in 2013. Most pitchers are ticking time bombs, but in Iwakuma there’s definitely increased risk.

Second, this 2013 performance isn’t necessarily out of the blue. His 2012 totals were dragged down by a 4.75 ERA and 1.42 WHIP over 30 innings in relief while as a starter, he posted a 2.65 ERA and 1.23 WHIP. Not otherworldly results as a starter, but his xFIP as a starter in 2012 was 3.61 and it’s 3.13 this season — so at least it’s in the vicinity of the same ballpark. Maybe outside in the beer garden.

And lest you’ve forgotten your history, there was a reason the Oakland Athletics bid $13 million bucks to just have the right to negotiate with him back in 2010. His record in Japan wasn’t Darvishian but over just about 1000 innings pitched, Iwakuma had a career 3.14 ERA and 1.19 WHIP, striking out 747 batters over that stretch.

But on to the how.

The best way I can probably describe it isn’t going to be terribly satisfying to many of you — but Iwakuma just appears to be a really smart pitcher. He knows his strengths and weaknesses and seems to just maximize situations in which he can pitch to his strength.

Here’s Iwakuma’s repertoire ( yeah, I know that doesn’t add up to 100%, he also throws a curve sparingly):

Fourseam 30%
Slider 19%
Splitter 21%
Sinker 23%

According to pitch values, each of these have been well above league average with his splitter being among the very best in the league (and, in fact, better than Yu Darvish). But yeah, it’s probably premature to be citing pitch values this early in the season.

Iwakuma doesn’t have an overpowering fastball. It sits right about 89-90 mph. But he uses it frequently as his first pitch in an attempt to get ahead in the count to set up the splitter. The fastball is his first pitch in almost 50% of at bats to left handed and right handed batters alike. If it’s not his fastball, he uses the sinker 30% of the time to lefties and his slider 30% of the time to righties. It’s almost never anything else.

When he’s behind in the count though, Iwakuma doesn’t just give in. Versus RHB, he’ll still go sinker/slider almost 60% of the time. Versus LHB, he goes to the sinker 50% of the time. Why does this matter? Well, because his fastball ain’t that great — and somehow, Iwakuma manages to induce batters into swinging at his junk (settle down, Beavis).

In all three-ball counts this season, with any combination of strikes, here’s the number of times he’s thrown his splitter and his sinker for strikes, and the corresponding percentage of swings:


For a guy with a 3.9% walk rate, Iwakuma isn’t looking to give up much in the way of free passes. Yet he’s very rarely throwing the ball in the strike zone in three ball counts while still inducing batters to swing at the crap almost three quarters of the time. Yahtzee.

With a little help from our friends at, we can see the percentages of swings in and out of the zone:


So he’s generating almost as many swings outside of the zone (low and away to lefties) as he does right down the middle. What’s perhaps more important are the swings and misses:


When Iwakuma is ahead in the count, he’s been practically unhittable. When ahead, he’s held opposing batters to a .152/.150/.276 slash line. He’s walked exactly zero batters and struck out almost 40% of them.

Obligatory gif’s:




You’re all sharp enough to look at the ERA predictors and surmise that he’s not likely to continue to post a sub-2.00 ERA, but the fact is that if Iwakuma can stick with the same recipe every fifth day, he’s probably going to be very effective. Because there’s not a lot of guesswork going on about what he’s going to throw in the count — hitters ought to know this by now and adjusted — and it’s still not enough to square up many balls. Depending on the return, you could certainly venture to sell high, but if I’m an Iwakuma owner, I’d cling to him.

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Michael was born in Massachusetts and grew up in the Seattle area but had nothing to do with the Heathcliff Slocumb trade although Boston fans are welcome to thank him. You can find him on twitter at @michaelcbarr.

22 Responses to “Don’t Fall Behind Hisashi Iwakuma”

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  1. Jason Castro's mother says:

    Is he a keeper over Kris Medlen? Alex Cobb? Homer Bailey?

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    • jst1vaughn says:

      It’s hard to buy him as a keeper because he’s so old. I have him in a keeper league, and despite his great season, I can’t even think about rolling him over, because he’s 32. Maybe I’m wrong, but I just don’t see him having.3-4 more years like this one. I’d rather roll the dice on someone younger.

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    • Kip says:

      To me, Iwakuma is a tough one to project due to MLB SSS (I realize the same could be said for other guys you mentioned). However, I would go Bailey, Cobb, Medlen out of those three if that helps at all. That’s just me.

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    • Kip says:

      small sample size.

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    • rpt says:

      Honestly, coming from a Bailey owner and fan, I’d have to say yes. Iwakuma is 32. He’s not young, but he’s not old, and theres no real reason to think he should be declining any time soon.

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    • FeslenR says:

      over Bailey

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  2. Ethan says:

    Isn’t it physically impossible to walk a guy when ahead in the count?

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    • David says:

      I could be wrong, but I believe this means “in all plate appearances in which he was ahead in the count at some point”

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  3. Mister says:

    So, Iwakuma has been successful in large part due to getting batters to swing at pitches outside the zone. The question is, why is that? Is his stuff really that filthy that he is just about to consistently fool batters with the splitter and slider? Or, is it just that batters are still unfamiliar with him and will soon adjust and stop swinging so much at these pitches out of the zone?

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    • Freakshow says:

      The author gave his theory. Its that he’s smart enough to know which pitch to use to get the outcome he needs.

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    • Feeding the Abscess says:

      He pitches aggressively in the strike zone to get ahead of hitters, and his sinker and splitter are thrown with only a 3 or 4 MPH difference. Add in that his sinker also has fairly significant downward movement, hitters can’t decide if they’re seeing a sinker that will hit the strike zone at the bottom of the knees or a splitter that will drop substantially further.

      His slider and curve are also decent, and while he can’t reach back and hit 95+ like Darvish, his 4 seam can reach 92-93. I guess you could say that he’s a lot like Darvish, if Darvish pounded the strike zone and couldn’t hit 95+.

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  4. Daven says:

    Iwakuma’s pitch count this year has been under 100 pitches not because of his shoulder, but because of a blister he had on his finger up until a few starts ago. Once the blister needed drained during the game, he was only good for something like another inning. So while he was still pitching reasonably deep in games given his pitch count at the time, he wasn’t getting anywhere close to 100 pitches.

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  5. Kip says:

    Can someone please do a write-up on Mr. Ervin Santana and/or please tell me whether he is a perfect sell-high? Thanks!

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  6. RPT says:

    I live in Seattle and have watched Iwakuma pitched extensively. I’m also a D1 college baseball player who just recently graduated, and I once faced a guy that reminds me of Iwakuma and despite not having filthy stuff, he was one of the toughest pitchers I’ve faced. My theory on why they are both tough to hit is the same: Timing. Iwakuma has a hitch in his motion, much like the aforementioned pitcher, and it makes it EXTREMELY difficult to time them correctly. I don’t think that is the sole reason for his success, but combined with his good command and deep repertoire I think it has a lot to do with it. He’s a boss, I wouldn’t sell him unless you get a crazy deal.

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  7. Coach says:

    I picked him up after week 1 – and with the RP/SP eligibility, he’s even better. I think I’ll have to keep him, because nobody is going to ‘buy high’ on him – and I don’t expect him to fall off a cliff.

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  8. Shawnuel says:

    Iwakuma has been one of the best pitchers in baseball over his last 162 games. With command/junk guys age is less of a factor. I’d go Bailey>Iwakuma>Cobb>Medlen.

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  9. Ed Nelson says:

    He works really fast too. I’ve seen so many hitters get down 0-2 on him in what seems like 10 or 15 seconds and they step out of the box and kind of shake their heads trying to figure out what happened. At that point it’s already too late. Eventually, guys are going to start swinging aggressively early in the count. It will be interesting to see if hitters can get to him that way and how he adjusts.

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