Japanese Hitters in the Major Leagues

It seems to me that at the end of the 2008 season, we have had enough seasons from Japanese hitters who have played regularly in the U.S. major leagues to crunch the numbers and see how their performance in the U.S. compares with their performance in Japan. The following are each Japanese player who has played regularly in the U.S. with his career Japanese numbers first, followed by his major league numbers, and below that the difference in performance between NPB and the major leagues. The statistical categories provided are as follows:

     (Age)  ABs     Hits    HRs  HR/100AB    BA  OBP  SLG  OPS
HR%  +/-BA  +/-OBP  +/-SLG  +/-OPS

Ichiro Suzuki
(18-26)  3619   1278    118  3.26     .353    .421    .522   .943
(27-34)  5460    1805     73  1.34     .331    .377    .430   .807
		                                 41.0%  -.024   -.044   -.092  -.136

Hideki Matsui
(19-28)	4572  1390    332  7.26     .304   .413   .582  .995
(29-34)  2892   852     112  3.87     .295   .371   .478  .849
                                                 53.3%  -.009 -.042 -.104  -.146

Kazuo Matsui
(19-27)  4638   1433  150  3.23    .309    .361    .486    .847
(28-32)  1755     486    23  1.31    .277    .331    .395    .727
                                                  40.5% -.032  -.030   -.091  -.120

Akinori Iwamura
(19-27)  3580   1073  188  5.25     .300    .366   .519    .885
(28-29)  1118     312    13  1.16     .279    .353   .394    .747
                                                  22.1% -.021  -.013  -.125   -.138

Tad Iguchi	  
(22-29)  3175  860  149  4.69    .271    .349    .471    .820
(30-33)  1841  494    44  2.39    .268    .338    .401    .739
                                                 50.9%  -.003  -.011  -.070   -.081

Kenji Johjima
(19-29)  4031  1206  211  5.23    .299   .360   .517    .877
(30-32)  1370    372    39  2.85    .272   .313   .412    .725
                                                  54.4% -.027  -.047 -.105   -.152

So Taguchi
(22-31)  4094  1134  67   1.64    .277    .333   .387  .720
(32-38)  1358    379  19   1.40    .279    .332   .385  .717
                                                 85.5%  .002  -.001  -.002  -.003

(Taguchi has an almost equal number of AB’s against right-handers and lefthanders in the U.S., and his BA, OBP, SLG and OPS are all within a few points of each other, which makes his performance in the U.S. especially surprising since he has apparently not benefited from more platoon play in the U.S.)

Tsuyoshi Shinjo
(19-28, 32-34)  5163  1309 205  3.97       .254   .305   .432    .737
(29-31)               876    215   20   2.28       .245   .299    .370   .669
                                                              57.5%   -.009 -.006   -.062  -.068

Kosuke Fukudome
(22-30)	3852  1175 192   4.98   .305   .397   .543    .940
(31)         501    129   10   2.00   .257   .359   .379    .738
                                                  40.0% -.048 -.038  -.164  -.202

Here are average and mean changes of these nine players, taken individually, going from Japan to the U.S.:

HR%
Average:  49.4%
Mean:     50.9%

+/-BA
Average:  -.019
Mean:     -.021

+/-OBP    
Average:  -.026
Mean:     -.030

+/-SLG
Average:  -.091
Mean:     -.092

+/-OPS    
Average:  -.116
Mean:     -.136                  

Let’s look at the totals:

		AB       H        HR       HR%        BA       OBP    SLG       OPS    
Japan          36,724    10,858  1,612    4.39          .296      .367    .494       .861
U.S.            17,171      5,044     353    2.06          .294      .356    .416       .772
			                       46.8%      -.002     -.011   -.078     -.089

Without Icharo (who by himself has had 32% of all U.S. at-bats by Japanese players)

		AB	H        HR         HR%       BA        OBP    SBG      OPS
Japan 	       33,105     9,580  1,494    4.51          .289        .361   .491        .852
U.S.            11,711     3,239     280    2.39          .277        .346   .410        .756
				          53.0%       -.012      -.015  -.081       -.096

The total-of-all-players numbers are a bit skewed and probably are less meaningful than the average and mean numbers provided above. For example, Shinjo’s .305 OBP in 5,163 NPB at-bats makes the difference in OBP between Japan and the U.S. a lot smaller than it really is.

So what conclusions can we draw from what is obviously a small, but not entirely insignificant, data set?

For one, Japanese players drop a LOT of power when they come to the U.S., but they maintain much more of their ability to get on base. This means that unless the Japanese player has Godzilla power, Japanese power hitters are likely to disappoint in the majors. It is worth noting that power and on base percentage are skills that tend to increase as a player gets older, while speed and batting average tend to decline. Since the Japanese players coming to the U.S. tend to be in the latter half of their careers (the median age for their first years in the U.S. of these nine players is 29.33), the obvious conclusion is that it is probably twice as hard to hit homeruns in the majors as it is in NPB.

The decline in on-base percentage is much less substantial, with an average drop-off of probably 25 or 30 points. This means that a Japanese player with a career .400 OBP in Japan could reasonably be expected to have an OBP in the U.S. in the neighborhood of .370, which is still excellent. It seems likely then that a high OBP should be a prerequisite for a major league team considering whether to sign a Japanese hitter.

One thing I noticed in preparing this piece, which is not shown in the numbers above, is that the Japanese players, like their career major league counterparts, decline significantly as a group starting with the year they are 32. For example, after fine years at ages 30 and 31, Tad Iguchi and Kenji Johjima both hit very poorly at age 32. The upshot is that I do not expect Kosuke Fukudome, who will be 32 in 2009, to justify his large contract over the next three years. He was a great player in Japan, but it looks like he came to the U.S. about two years too late to become a great player in the U.S.