Do Professional Asian Pitchers Go Through the Same MLB Learning Curve?

Zachary D. Rymer@zachrymerMLB Lead WriterFebruary 28, 2014

New York Yankees starting pitcher Masahiro Tanaka throws a pitch during spring training baseball practice Friday, Feb. 21, 2014, in Tampa, Fla. (AP Photo/Charlie Neibergall)
Charlie Neibergall/Associated Press

This Saturday will be bigger than most spring training Saturdays. As reported by Wallace Matthews of, fans are finally going to get a glimpse of Japanese ace Masahiro Tanaka on the mound in a New York Yankees uniform.

It's an important occasion mainly...well, alright, mostly because the Yankees paid $175 million to acquire Tanaka. In an offseason chock-full of big purchases, Tanaka was their biggest.

But then there's the other drawing force at work. We've heard all about the Japanese phenom's talent, but there's still that sense of mystery over his future in MLB.

He hasn't yet gone through the learning curve, as all professional Japanese pitchers must.

Ah, yes. The learning curve. You might also hear it referred to as the "adjustment period." By either name, it's a notion that's pretty much automatically applied to Asian professionals coming over to pitch in MLB, and that's the tricky part. 

The implication is that all pro Asian pitchers—which, to clarify, is a group that does not include pitchers signed as amateurs like Chien-Ming Wang, Chan Ho Park and Junichi Tazawa—fall under the same learning-curve umbrella. And here are two things about that:

  1. Based on things we know, they do.
  2. Based on other things we know, they don't.
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Like I said. Tricky. 

And this, I suppose, launches us into explanation time.

Why are all professional Asian pitchers in for a common learning curve when they come over here? 

It has to do with how baseball there and baseball here aren't quite the same. We've known that for a while now, but I for one feel like the differences have come to be a lot more out in the open than they used to be—especially when it comes to what separates MLB from Japan's Nippon Professional Baseball.

You can see Ron Darling and Eric Byrnes talking about one of the big ones in the video above: The baseballs in MLB are slightly bigger and not as tightly wound as the baseballs in Japan. 

Pitchers who come over to MLB from NPB have to adjust to throwing a different ball. No small task, that.

Anthony McCarron of the New York Daily News recently took things a little further by noting that MLB baseballs are not just bigger, but also less sticky. Darrell Rasner, who has pitched in both MLB and NPB, says the ball is "easier to manipulate" in Japan.

Then there's the fact that the mounds in Japan are softer than MLB mounds. The strike zone may also be more generous. Starting pitchers in Japan tend to pitch once a week rather than once every five days. And when they do, they face lineups that aren't as deep or powerful as MLB lineups.

The differences between MLB and the Korean Baseball Organization (KBO) and Taiwan's Chinese Professional Baseball League aren't as widely publicized. But since both leagues are generally considered to be inferior to NPB, at the least we know that the reality of MLB lineups being deeper and more powerful applies even more so to the KBO and CPBL.

All of this accounts for why it's OK to treat "the learning curve" for Asian professionals as something that actually exists. There are very real differences to adjust for, and success in the majors isn't going to happen unless those adjustments are made.

This is the end to which all the pitchers in question fall under the same learning-curve umbrella.

But now comes the inevitable catch: It's only the adjustments that Asian pros coming over to pitch in MLB have in common. If, how and when those adjustments are made is an entirely different story.


Ideally, we'd be able to use statistics to paint a picture of what the learning curve for Asian pitchers looks like: where it starts, where it ends, what shape it's in, etc. But to do something like that would require a large collection of clean data, and that's something that doesn't exist.

That's thanks largely to the reality that relatively few pitchers have been able to slide right into a defined role at the major league level. 

Hideki Irabu, for example, was brought along slowly by the Yankees in 1997, starting the year in the minors and making only 13 appearances (nine starts). Shigetoshi Hasegawa was in and out of Anaheim's rotation in 1997. 

Before Hisashi Iwakuma moved into Seattle's rotation late in 2012, he was serving in an undefined relief role. Koji Uehara began 2009 in Baltimore's starting rotation, but an injury limited him to just a dozen starts. When 2010 rolled around, he was a reliever.

These and other examples send mixed messages about the time it takes to learn how to pitch in the majors. If any group would have something more concrete to say on that point, it's the pitchers who have been thrown right into set roles and expected to produce right away at the MLB level.

The problem with that idea, again, is that not enough have been, and the ones who have largely went in their own directions.

Between pitchers from Japan, Korea and Taiwan, only nine have come right over and made as many as 25 starts in the majors as rookies. If there was a set learning curve, you'd expect it to be clearest in the monthly splits of their rookie seasons. Maybe initial struggles in April followed by smoother sailing. Or smooth sailing at the beginning, struggles in the middle, and then back to smooth sailing. 

But if we use FanGraphs to break it down by FIP—that's Fielding Independent Pitching, which is preferable in this case because it's not as luck-dependent as ERA—we see that no such clarity exists.

Monthly FIP Splits of First-Year Asian Starters
Hideo Nomo199528(Strike)4.072.372.383.422.36
Masato Yoshii1998293.625.505.284.653.354.12
Kazuhisa Ishii2002282.833.895.236.426.286.65
Daisuke Matsuzaka2007322.914.682.564.985.035.22
Hiroki Kuroda 2008314.243.826.492.752.933.06
Kenshin Kawakami2009256.242.664.366.133.183.17
Wei-Yin Chen2012323.714.294.703.784.255.51
Yu Darvish2012293.314.633.384.072.941.89
Hyun-Jin Ryu2013302.783.644.103.632.343.25

Since there are a lot of numbers up there, I've tried to make things easier by highlighting pitchers who you could say went through some sort of monthly learning curve: Hideo Nomo, Masato Yoshii, Hiroki Kuroda, Kenshin Kawakami, Yu Darvish and Hyun-jin Ryu. 

Improved control was a huge part of Darvish's 2012 turnaround, as he walked no more than two in any of his last seven starts.
Improved control was a huge part of Darvish's 2012 turnaround, as he walked no more than two in any of his last seven starts.Mark J. Terrill/Associated Press

Only two of those curves, however, come close to resembling each other: those belonging to Kawakami and Darvish. The ups and downs they went through in the first four months of the season look different, but it does catch the eye that both turned a corner in August and September.

The trouble is that Kawakami actually produced his strong September while working as a reliever (he's in the mix anyway because he had started in each of the previous five months). Also, his strong finish didn't end up going anywhere. He soon washed out of the majors after 2009, which makes the tail end of his '09 curve look even more like a fluke.

Kawakami's not the only one of the highlighted guys who didn't take off after his rookie season. By fWAR and many other measures, Nomo never topped his first season. Yoshii peaked in his third season, but he did so with a 5.86 ERA and 5.55 FIP. We'll see about Ryu, but the way in which Kuroda continued to impress after his first season and Darvish impressed mightily after his first season makes them look like special cases.

As for the other three guys who aren't highlighted, you don't see anything really resembling a curve when you look at their monthly splits. You see an ugly uphill climb in Kazuhisa Ishii's case, and a series of ups and downs in the other two cases.

And while Ishii and Daisuke Matsuzaka figured things out in their second seasons according to ERA, they didn't so much according to FIP. Ishii's 4.73 FIP in 2003 was nearly a full run higher than his 3.86 ERA. Dice-K's 4.03 FIP in 2008 was more than a full run higher than his 2.90 ERA.

With no easily discernible learning curve in place with the starters, we move on to the relievers. But if we do the same thing with the seven Asian pros (all Japanese) who have made at least 50 relief appearances as rookies in the majors, we get a similar picture:

Monthly FIP Splits of First-Year Asian Relievers
Kazuhiro Sasaki2000635.635.133.934.424.103.13
Akinori Otsuka2004731.901.913.425.781.302.86
Shingo Takatsu2004593.483.133.392.836.233.56
Takashi Saito2006722.303.690.492.381.960.30
Hideki Okajima2007662.292.782.563.323.906.99
Masa Kobayashi2008572.654.494.816.347.133.13
Hisanori Takahashi2010532.243.045.763.892.023.08

Once again, the players who went through something resembling a learning curve are highlighted. And while there are plenty of them, you still don't see any striking similarities between the individual curves.

There's also a lack of post-rookie patterns here, too. Takashi Saito, Hisanori Takahashi and Hideki Okajima peaked as rookies. Kazuhiro Sasaki peaked in his second year. Akinori Otsuka peaked in his third year. Neither Shingo Takatsu nor Masahide Kobayashi lasted to a third year after flaming out in their sophomore seasons.

So all told, when you look at the guys who have been tasked with learning how to pitch in MLB on the fly, the message is twofold: On the one hand, it is possible to learn how to pitch via a learning curve. But on the other hand, there's no point in anticipating a learning curve according to a specific timetable.

If it's going to happen, it's going to be suited to the individual.

Because of the tangible adjustments the transition requires, it's still fair to talk about "the learning curve" in regard to professional Asian pitchers making the leap to MLB. They're not trading one identical copy of the game for another identical copy of the game, after all.

But when it comes to what happens next, all history tells us is that all bets are off. Though they face common questions when they come into the league, professional Asian pitchers are going to provide their own solutions.

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