Hisashi Iwakuma and the Other Road to Elite

Hisashi Iwakuma is perhaps the most underrated pitcher in baseball. Since his debut in 2012, he has posted an xFIP of 3.24: good for 12th-best among qualified starters, and bracketed on either side by Max Scherzer and Madison Bumgarner. The former of that duo just signed a well-publicized seven-year, $210 million dollar contract; Iwakuma is on the last year of a three-year deal worth a total of $20 million.

Iwakuma won’t make Scherzer money in free agency next year, mostly due to the fact that he is four years older than the new Nationals right-hander, but it gives us an idea of the company he’s kept for the past three years. Always the groomsman, never the groom, Iwakuma lives with his near elite-level production in the shadow of perennial Cy Young candidate Felix Hernandez: while he finished third in Cy Young voting in 2013, he is usually forgotten when the final lists of best pitchers are made — left instead to plan the year-end parties for the King.

Make no mistake — he’s on that list, and it’s not because he can throw 96 MPH, or has a ridiculous breaking ball. Iwakuma is one of those guys who does everything really well with minimal flash, like controlling the running game and limiting walks. Today we’re going look at some of those parts, identify why he’s so successful, and compare his peripherals to pitchers in the last 10+ years. Hopefully that final point will show us how far a pitcher with his peripheral numbers can go.

We’re going to be focusing mostly on strikeout, walk, and ground ball rates. Pitching is a complicated pursuit, and there’s a lot that goes into being successful at it, but I like to think these rates make up the primordial ooze from which pitchers accrete. This is also for simplicity’s sake, as we can compare these statistics very easily with pitchers in the past. First, let’s look at Iwakuma’s 2014 league rank among starters with a minimum of 150 innings in K%, BB%, GB%, and xFIP:

	2014 Iwakuma	2014 Rank
K%	21.7%	31st
BB%	3.0%	2nd
GB%	50.2%	23rd
xFIP	2.85	9th

At first glance, these numbers don’t scream ace. Very good, yes, but other than his walk rate and great xFIP, nothing pops out. However, we shouldn’t breeze over his BB%: that walk rate puts him in some rarified historic company, and it’s absolutely the driver of the improvement he’s shown since coming into the league. Let’s look into that.

Overshadowed by the incredible control year Phil Hughes had in 2014 was Iwakuma’s only slightly less incredible control year: in a ranking of BB/9 for pitchers with at least 150 innings from 1920 on, Hughes ranked 4th (.69 BB/9) and Iwakuma came in 31st (1.06).

If that sounds unimpressive, consider the pitchers surrounding Iwakuma on the leaderboard:

• Greg Maddux (26th, 1.04 BB/9, 1996)
• Juan Marichal (29th, 1.05, 1966)
• Hisashi Iwakuma (31st, 1.06, 2014)
• Roy Halladay (34th, 1.08, 2003)

Walk rates have trended downward recently, so historical comparisons have to be taken be taken with a small grain of salt, but these are household names around him. As we’ll see, that fact becomes less and less surprising.

While it’s obvious that walk rate is not an indicator of success as a standalone statistic, there’s no denying the track records of pitchers who limit free passes to an absolute minimum. There are some fun facts in this area of Iwakuma’s game: he only had 13 3-0 counts in all of 2014, walked only 21 batters in 28 games, and hit only two batters (in the same inning, strangely, back to back). Only Phil Hughes was more pinpoint with his control, and Hughes set a major league record last year (best strikeout to walk ratio) that was predicated on being pinpoint with his control.

Add strikeout ability to historic control numbers, and you begin to have the makings of something special. Iwakuma’s arsenal is pretty diverse, as he possesses a four-seam fastball, sinker, curve, slider, cutter, and splitter. The sinker, slider, and splitter are his main pitches, and it’s the split that does the most damage. His fastball velocity is nothing at all to write home about: it averaged in the high 80’s during 2014. However, anything paired with the splitter is going to be effective, mostly because the splitter does this:

In this example as in many others, good readers, the splitter generates a half-swing, and Zunino doesn’t even manage to catch it cleanly. There are some great posts from the past on the specifics of Iwakuma’s splitter, so I’ll just say this: it’s one of the best in the game, and he throws it a lot for a reason. In 2014, it generated a 28% whiff rate — slightly below-average for a split — but an incredible 67% ground ball rate. Only Huroki Kuroda’s was better by normalized run value last year for pitchers with over 150 innings (yes, I do remember Tanaka).

That ground ball rate is the final piece of the puzzle, and is the trait that sets him apart from an otherwise-similar control pitcher like Phil Hughes. With an extremely limited number of walks, strikeout ability, and an above-average ground ball rate driven by the splitter, Iwakuma had a very special 2014.

How special? To find out, I’ve taken the K%, BB%, and GB% for all pitchers with over 150 innings since 2002 and created z-scores for each category to compare to Iwakuma’s rates. I then summed the z-scores to get an overall comparison score based on all three rates.

Basically, the closer the comparison pitcher is to zero, the more like Iwakuma they are in terms of walk, strikeout, and ground ball profile. Each increment of one in the comparison score is a standard deviation away from Iwakuma, who resides at zero. Let’s take a look at who comes up:

Year	Pitcher	K%	BB%	GB%	Comparison Score
2014	Hisashi Iwakuma	21.7%	3.0%	50.2%	–
2010	Roy Halladay	22.1%	3.0%	51.2%	0.24
2009	Roy Halladay	21.6%	3.6%	50.2%	0.32
2013	Adam Wainwright	22.9%	3.7%	49.1%	0.79
2011	Roy Halladay	23.6%	3.8%	50.9%	0.93

Needless to say, this is pretty good company: Roy Halladay won the Cy Young in 2010, finished 5th in 2009, and 2nd in 2011. Adam Wainwright came in 2nd in the voting in 2013, mostly because Clayton Kershaw is a robot. While we know the voting process does have its drawbacks (ahem), the point is that pitchers who have elite walk suppression paired with this profile of ground balls and strikeouts are extremely successful by almost any measure.

As I said before, this is a simplistic way of breaking down a pitcher. There is more to the art and science of pitching than three categories of rate statistics. However, what we do see is that pitchers cut from this cloth succeed, and generally succeed greatly. Iwakuma has always had the strikeout and ground ball ability, and in 2014, he decimated his walk rate. That was a huge step, and now the question pertains to that improvement holding alongside his other above-average skills.

Sample size stabilization says that walk rate changes over one season do hold weight, but we’ll have to wait and see. Iwakuma is 33, his velocity has decreased every year he’s been in the majors, and let’s face it: walking just one batter per nine innings is really difficult.

On paper, Hisashi Iwakuma has the profile of an elite pitcher. He doesn’t do it with an overpowering fastball, or a huge curve. That can go unrecognized unless we look a little harder, but there’s something special about that method: maybe even extra special.