Contextualizing Masahiro Tanaka’s Japanese Numbers

After a lengthy period of deliberation, the Rakuten Eagles officially posted Masahiro Tanaka on Christmas day. MLB teams have until Friday at 2PM PST to sign the Japanese starter. It is expected that the Dodgers will be among Tanaka’s top suitors, due to their large checkbook and Josh Beckett‘s questionable future. The Yankees, Diamondbacks, Mariners, Cubs, White Sox, and other teams are also involved. Tanaka will likely command a very high price tag due to his age (25 in November, younger than most free agents to hit the free market) and since signing him does not require a draft pick.

Tanaka’s ERA in Japan is a stat that really sticks out; 1.44 over the last three seasons. It’s the first thing to come up in stories about him. However, the run environment in Japan is different than it is in the US, so ERAs between countries are not directly comparable. Recent changes to the ball and the different type of play in Japan has lead to large run environment fluctuations as well:

Tanaka_NPBRunsChart

Even here, ERA doesn’t mean much without including the run environment and the impact of the pitcher’s home ballpark. We also have not heard much about Tanaka’s peripheral numbers (FIP, etc).

In order to see how Tanaka’s numbers compare to the rest of NPB, we’ll need to use league and park adjusted statistics. ERA- compares a player’s ERA to their league average and includes the impact of their park*. Given the park factor information found in the footnotes, Tanaka’s ERA- can be found. Since Tanaka’s peripherals can be found on baseball reference, his FIP** and FIP- can be calculated as well. The point of this exercise is not to scout the stat line, but to contextualize Tanaka’s dominance in Japan.

Here is a summary of these calculations:

Year IP ERA ERA- FIP FIP-
2007 186.1 3.82 107 3.21 89
2008 172.2 3.49 88 2.82 71
2009 189.2 2.33 57 2.81 69
2010 155 2.50 62 3.02 75
2011 226.1 1.27 42 1.50 50
2012 173 1.87 61 1.28 41
2013 212 1.27 35 1.98 54

Now that we have these statistics, what do they actually mean? To find out, let’s compare Tanaka to somebody familiar. Clayton Kershaw is the best pitcher in MLB right now, is about the same age as Tanaka, and has been active over the same period. He also just posted the best ERA- by any Dodger starter since the end of the dead-ball era. Here’s a comparison of their adjusted statistics (lower is better):

Tanaka_KershawStatComparison

Kershaw’s numbers are in red and Tanaka’s are in blue. Tanaka’s adjusted numbers are significantly better in relation to his league average than Kershaw’s over the same period. It’s somewhat interesting that Kershaw and Tanaka have had very similar year-to-year patterns on their ERA- numbers, but it probably isn’t meaningful.

So, how do Tanaka’s best seasons (41 FIP- in 2012, 35 ERA- in 2013) compare to the best MLB seasons of all time? In the US, a full season for a starter with a FIP- of 41 would be the second best season since the end of the dead-ball era; slightly better than Randy Johnson‘s 45 FIP- in 1995 but well behind the record 30 FIP- posted by Pedro Martinez (who else?) in 1999.

Tanaka’s ERA- values have been even more impressive. His 42 ERA- in 2011 would be sixth-best in major league history (ahead of Dwight Gooden in 1985, behind Pedro Martinez in 1999). His ERA- in 2013 was 35.3, just behind Pedro Martinez’ record 35.0 ERA- in 2000. According to Fangraphs’ RA9 WAR, Pedro was worth a staggering 12.3 wins that season, and he only threw 5 more innings than Tanaka threw in Japan last year.

Tanaka has thrown three seasons in a row that would rank in the top 10 in MLB history by ERA- or FIP-. That’s really impressive, but it doesn’t mean much without seeing how common extreme values are in Japan. The following chart compares Tanaka’s NPB ERA- to NPB ERA- values for Yu Darvish and Kenta Maeda (who may be posted after next season):

Tanaka_NPBPitcherComparison

While Tanaka has the best single-season ERA- value of these three pitchers, Darvish had an ERA- of 36 in 2011 and Maeda had an ERA- of 41 in 2012. Extreme ERA- values, such as the ones that Tanaka has posted over the last few seasons, do not seem to be very unusual in NPB right now. All three pitchers have had seasons that would rank among the all-time best MLB seasons in the very recent past.

Darvish had slightly worse peak adjusted stats in NPB than Tanaka, but that doesn’t mean that Tanaka will be better in the MLB. Most scouts say that Darvish is better in the MLB than Tanaka will be. However, it’s still fun to see how dominant Tanaka was in Japan. He concluded his Japanese career by winning the Nippon Series, further cementing his legacy. It’s hard to see what else he would have been able to accomplish there. Whichever team signs him this week is certainly hoping that he will have similar results in America.

Footnotes

* Park factor methodology: I used the park factors found here: http://subjspeak.blogspot.com/2012/12/npb-park-factors-for-2006-2012.html

A few unresolved questions from this article led to assumptions when making park-adjusted calculations in the main post body (attempts to reach the author of the post failed). The article does not state if the park factors presented are for the stadium or for the team, so I assumed they were for the stadium. This moves the park factors closer to neutral when applying them to the players, since the player’s away games will be in an approximately league average environment.

Assuming that the numbers in that post are for the stadium produces a 35.3 ERA- for Tanaka in 2013, as is shown in the post above. If it is used as a player park factor (opposite assumption), his ERA- would improve to 34.9. Darvish’s 2011 ERA- would increase from 36.4 to 37.4 if using the opposite assumption. Maeda’s 2012 ERA- would increase from 41.5 to 42.1. The magnitude of these changes are pretty small, but worth mentioning since I’m not 100% confident in this method.

The data in the NPB park factor post is also missing data for the 2013 season, so I assumed that the Hiroshima and Rakuten park factors remained the same as their 2012 values. Those park factors have both been steady for the last few seasons, and regression/weighting would heavily favor the previous stable period if there was a change this year. Since the same regression assumption cannot be made for missing park factor data prior to 2006, I removed Darvish’s 2005 ERA- from the NPB comparison chart.

** In order to calculate FIP for Tanaka, the MLB weights (13*HR, 3*BB/HBP, 2*K) are used. It’s possible (likely?) that the weights given to these statistics should be different for NPB. Using the same equation for both leagues is a convenient way to compare pitchers in different environments, like what is done between Kershaw and Tanaka above.

This post uses the following statistics:

  • ERA: Earned Run Average.
  • ERA-: ERA, park adjusted and compared to league average. 100 ERA- is a league average pitcher by ERA, 90 ERA- is 10% better ERA than league average, etc. Explanation here.
  • FIP: Fielding Independent Pitching. Attempts to create an ERA-like number using only plays that do not require defense to complete (K, BB, HR) by assuming the pitcher is playing in front of a league average defense. Explanation here.
  • FIP-: FIP, park adjusted and compared to league average. 100 is a league average pitcher by FIP, 90 is 10% better FIP than league average, etc. Explanation here.
  • RA9 WAR: Pitcher wins above replacement, calculated using the runs a pitcher allows as the main metric (combines fielding independent and fielding dependent metrics). Explanation here.

About

Daniel Brim grew up in the Los Angeles area and remains a Dodger fan despite currently residing in Salem, MA. As an engineer, he’s fascinated by the math and science behind the game of baseball, which probably explains a lot. He started “Blog To The Score” in late 2013 to dig deeper into the numbers behind the Dodgers. In its brief lifespan, it gained attention from local and national media. You can find him spending too much time in the comments section or on Twitter.


646 comments
Weston T
Weston T

Guy on MLB Network just said Tanaka is gonna sign Friday? Hmm.

Weston T
Weston T

Besides the Dodgers, I honestly can't wait for fantasy baseball. Drafting is one of my favorite days of the year, probably more so than my birthday.

Lobo
Lobo

This is getting ridiculous.  Remember how I mentioned there's a guy at my work who keeps selling Nintendo Wii's for like 50 bucks?  Well today he has a brand new in box Mario Kart Wii bundle, a Quad Charging station for Wiimotes, and a brand new Zelda edition 3DS XL with Link Between Worlds pre-downloaded and the standard 4GB memory card replaced with an 8 GB one.  Seriously approaching black market territory here

steelmohawk
steelmohawk

no snow day here in DC, unless you are Marion Barry.

Jeremy_N
Jeremy_N

@DBrim I have heard people say he would chose by Tuesday or Wednesday so that he could complete a physical before the deadline Friday. So it makes sense that he would have decided.

Weston T
Weston T

Disregard, was unaware Friday was the 24th

Jeremy_N
Jeremy_N

@Weston Taylor im an avid fantasy football player, but I had to give up on fantasy baseball because I always value dodger players too highly and lose. just cant get over being a fan. also, I could never have a giant on my team under any circumstance.

Haikairu
Haikairu

@Weston Taylor Yep. Stoked for fantasy. This time I want to be there for draft and not auto draft. Though, picking up players and cobbling together a team of guys nobody wanted and taking them to the championship game felt very Oakland.

Haikairu
Haikairu

@Lobo The fact that he has things is black markety?

DBrim
DBrim moderator

Hits us this evening.

Jeremy_N
Jeremy_N

@Lobo@DBrim if the money is the same, why would his agent tell him to pick the cubs?

Weston T
Weston T

I'm gonna have to do the same thing this season. I traded away my first five draft picks minus my fourth for a championship last season.

Lobo
Lobo

@DBrimfan1987 @Lobo Not that he has things.  That he ALWAYS has things that he sells for less than what they're worth.  I'd estimate that in my time here the guys has had probably 10-15 different Wii's that he's sold.  I bought mine from him my first term here in Fall 2012.  And it's in perfect working condition, few scratches but that's it.  Got it from him for 50 bucks.  Last week he had TWO PS3's that he was selling for less than they were worth.

steelmohawk
steelmohawk

@DBrim it started earlier this morning, it seems they might send us home early, which figures because I finally was scheduled to have work today.

Haikairu
Haikairu

@Lobo @jneil @DBrim That's not really that ownership group's style. But these kind of opportunity rarely come around.

Jeremy_N
Jeremy_N

@Lobo@jneil@DBrim if the cubs did that then I could see him picking them. however, I just don't see the cubs doing that. I don't think they would be willing to eat $20+ million for him this year when they have only a remote shot at making the playoffs. I think they are focused on 2015 as the first reasonable possibility of making a run.

Lobo
Lobo

@jneil @Lobo @DBrim I don't think the money is the same.  I think the Cubs will outbid everyone by at least 20 million

Lobo
Lobo

@DBrimfan1987 @Lobo I can respect that.  As I said, it's by no means a bad game.  A lot of it just comes down to personal taste here

Lobo
Lobo

@DBrimfan1987 @Lobo It's possible that coming at it so late like I am it just isn't grabbing me as much.  I do appreciate the detail put into it but I just feel the dark tone was done better in Twilight Princess, which also managed to capture the sense of adventure that keeps me coming back to Zelda games again and again.  And parts of the game stress me out for no reason.  Like the alien sidequest, I know mos t people think it's a lot of fun but for some reason it really stressed me out.

Haikairu
Haikairu

@Lobo Actually, my bad, it was released in 2000.

Weston T
Weston T

I always enjoyed mauling everything with the Goron mask on. If nothing else, that was cool.

Lobo
Lobo

@DBrimfan1987 @Lobo I figured, but I knew that it's one of your favorite games so I wasn't sure if you were serious or not

Haikairu
Haikairu

@Lobo @DBrimfan1987 I appreciate Majora's Mask for its dark themes, and it's vibrant world. In 2001, when the game was released, Clock Town was amazing. It felt like a living breathing place. Characters had routines and  interacted with other characters, irrespective of your actions. Little stuff like that makes it amazing.

Haikairu
Haikairu

@Lobo @DBrimfan1987 Just pulling your leg, homie. That's the kind of thing people say in the comments on a game blog when you dislike a game that they like.

Lobo
Lobo

@DBrimfan1987 @Lobo What am I doing wrong?  I'm getting every mask, every heart piece.  Every conceivable thing to do in the game I'm trying.  It's just not a particularly fun experience.  None of the dungeons are particularly good so far (I just finished Great Bay Temple), the bosses are subpar, and there's no new interesting items other than the masks.  And with the masks, the only ones that are particularly fun are the Goron mask and the Zora mask.  The bunny hood is useful, sure, but it's not fun.  It's a perfectly good game but it's not one I'm enjoying my time with

Weston T
Weston T

Your new user names are hilarious.

Lobo
Lobo

@DBrimfan1987 @Lobo By the way, I'm doing a full playthrough of MM for the first time and it's really just not doing it for me.  I'm not having anywhere near as much fun as I normally do in a Zelda game

Lobo
Lobo

@DBrimfan1987 @Lobo Possible.  How about the Zelda 3DS XL though?  He's selling it for $210 which is pretty much exactly what it retails for

Haikairu
Haikairu

@Lobo @DBrimfan1987 Retailers like Best Buy and Gamestop give you practically nothing when you trade something in and then make huge profits. Maybe he buys stuff at more reasonable prices for sellers and then turns around and sells it for low margin profits.

Lobo
Lobo

@DBrimfan1987 @Lobo Also, 50 bucks wouldn't surprise me if he were just selling HIS used Wii.  But getting ahold of like 10 of them?

Lobo
Lobo

@DBrimfan1987 @Lobo Maybe it's not but it seemed high to me considering it came with a Wii Motion Plus controller, a Gamecube controller, and Mario Kart Wii

steelmohawk
steelmohawk

@DBrim everyone is bailing, could be a short day, maybe probably going to clean up some of my brewing supplies and plan for the weekend.

DBrim
DBrim moderator

At least snowstorms let me lock myself in my apartment so I can write.

DBrim
DBrim moderator

At this time yesterday, forecast was 2-4". Now it's 8-10".