Tag Archives: win shares

The months matter

A recent discussion in the “Hey Bill” feature in billjamesonline discussed why some players do better than others and brought up the topic of relative age effects. I did a study about 10 years ago about the effects of NPB players’ birth months that was published in the Daily Yomiuri, which means it’s disappeared from the web. The upshot of that study was that players born from April 2 to June 30 are over-represented in the NPB amateur draft and, on average, have less valuable careers than player born from July 1 to April 1–the cutoff date for school admissions.

Children born on April 1 will enter school in Japan a year before a child born the following day.

Overview

I replicated the study using every domestic player signed by an NPB team from the end of the 1965 season through the start of the 1997 season. Omitting four players I don’t have birth dates for, that remaining group of 2,160 players contains two active players, Ichiro Suzuki and Kazuya Fukuura. And whatever they produce in 2019 is not going to affect anything one way or another. The starting point of the study was set by the introduction of NPB’s first draft in 1965.

Breaking down each quarter of a year by birth month — with April 1 counting as March — and draft round. The most populous cell is the 127 signed first-round picks signed who were born from April to June. The second most is the 121 players born in those months taken in the second round. As expected, the 341 “haya umare” or early-born players whose birthdays go from Jan. 1 to April 1, make that quarter the least populous.

The table below gives the career win shares produced by players born in each quarter and the total number in each group, without reference to draft round.

The last thing that needs to be mentioned is the problem of value in the major leagues. Major League win shares are given 20 percent more weight in the calculations. It’s just a guess. They could be 50 percent more valuable for all I know.

Distribution of domestic players by birth-month quarters

Apr-JunJul-SepOct-DecJan-Mar
Avg WS210.0230.5306.8223.0
Number754651414341
Percent of total34.930.119.215.8

The favoritism in the draft show players born in the April-June quarter is exacerbated by an even higher share of those players taken in the first two rounds, and by the performance of those players.


Value rank of birth-month quarter by round

RoundQuarter starting Avg WS Best career
1stJuly68.8Kazuhiro Kiyohara, 1B
1stJanuary60.2Masaki Saito, P
1stOctober59.7Koji Yamamoto, CF
2ndOctober55.6Taira Fujita, SS
3rdOctober54.7Hiromitsu Ochiai, 1B
2nd January48.1Hiromitsu Kadota, DH
1stApril44.6Hideki Matsui, CF
2ndJuly44.5Keishi Suzuki, P
4thOctober39.0Ichiro Suzuki, RF
3rdJanuary38.8Yoshihiko Takahashi, SS

Discussion

Another thing that needs to be mentioned is that the birth-month quarter starting in January is largely populated by pitchers and catchers. In my previous study, I found that more than a quarter of the players drafted as catchers were born between Jan. 1 and April 1.

When I first did this study, a number of people gave me what I’d snarkily call “baseball announcer explanations” for why players born from October to April 1 outperform the players who are chosen more often by pro teams. The most popular one of these was, “Oh, they’re used to overachieving, so they try harder.”

All these guys try hard. I think there are three things going on.

  1. Accessibility
  2. Age bias
  3. Burnout

Accessibility

Players who are born after April 1 are larger and physically more developed than players months younger than they are. This gives them more time to play, more time to stand out and be noticed by coaches, who select them to play so that they can be seen by scouts.

Age bias

Because players born from October to April 1 are less physically developed than the players they are competing against, they are less likely to dominate competitions when scouts are watching.


Burnout

This is something that hadn’t occurred to me until recently. According to people who know a lot about how youth baseball functions in Japan, many of the players who eventually turn pro in Japan are not the best in their age groups when they are young. Amateur sports in Japan are intense, year-round, meat-grinding wars of attrition.

The best players typically become pitchers, and because competition (with the exception of university baseball) is in single-elimination tournaments, those aces throw game after game until their bodies break down. They are then surpassed by those who were a step behind them a year or two earlier.

Many of Japan’s best pitchers were not aces in elementary school or junior high. Masahiro Tanaka was a catcher until high school. Koji Uehara ran track in junior high and was an outfielder until his senior year in high school, when his school’s ace, Yoshinori Tateyama began to break down from injury.

It is not that much of a stretch, then, to see many of those players born from April to June as being at the end of their physical tethers by the time the pros call on them.

I know I’ve talked about this before

If we make a top-25 of players in NPB’s draft era, the best single draft round was the first round of the 1968 draft, Hall of Famers Hisashi Yamada, Koji Yamamoto, a player who has curiously been overlooked for the Hall, Michio Arito, and another who will eventually make it, Koichi Tabuchi.

The second best group are three from the Fab 4, the fourth round of the 1991 draft, Ichiro Suzuki, Tomoaki Kanemoto and Norihiro Nakamura.

Genda and NPB’s best

It took a while for the Japanese language media to catch on to Sosuke Genda’s shortstop fielding records in 2018 because fielding data in Japan is considered even more esoteric than it is in the States, and I’m referring to just the basics, put outs, assists, errors, double plays, fielding percentage.

There’s really nowhere to scan a publicly available database and find out who had the most assists or putouts in an NPB season or in their career. Things are getting better, but it’s still to quote Mr. Spock, “Stone knives and bearskins.”

The data is out there, it’s just inaccessible. This year, NPB’s website (the Japanese language version) did us the great service of posting a player page for every past NPB player. Of course, this includes batting and pitching. When NPB was publishing its encyclopedia, it did not include fielding records.

So here are the top 10 Japanese pro baseball seasons by a shortstop ranked in terms of total double plays and then assists

YearLeagueTeamName RGPOAEDPField
2018PLLionsSosuke Genda14327152611112.986
1963PLHawksKenji Koike14729549323111.972
2008CLTigersTakashi Toritani14426347615107.980
1985CLCarpYoshihiko Takahashi13023946816107.978
1998PLMarinesMakoto Kosaka12323641716106.976
1981PLBravesKeijiro Yumioka13021044917104.975
1964PLHawksKenji Koike14928949836103.956
2007CLCarpEishin Soyogi13523143913103.981
1991CLSwallowsTakahiro Ikeyama1322704124101.994
2006CLTigersTakashi Toritani14621349021100.971
2001CLBayStarsTakuro Ishii14025241712100.982
2016PLFightersTakuya Nakashima14321944714100.979

Top 10 NPB shortstop seasons ranked by total assists

YearLeagueTeamNameGPOAEDPField
2018PLLionsSosuke Genda143271526111120.986
19481LDragonsKiyoshi Sugiura13726850245900.945
1954PLBuffaloesTakeshi Suzuki13221950144680.942
1964PLHawksKenji Koike149289498361030.956
1963PLHawksKenji Koike147295493231110.972
2001PLMarinesMakoto Kosaka14025249216990.979
2006CLTigersTakashi Toritani146213490211000.971
2000PLMarinesMakoto Kosaka13522648911980.985
2003PLMarinesMakoto Kosaka1342264838860.989
2017PLLionsSosuke Genda14322848121890.971

Other than Genda, the big name on this list is Kenji Koike of the Nankai Hawks. Bill James’ win shares credits him with having four of the six most valuable defensive seasons at shortstop in the history of pro baseball in Japan. Koike’s rival for the title of Japan’s greatest shortstop is Hall of Famer Yoshio Yoshida, who had more career value at the position but did not reach the amazing peaks Koike did.

Genda’s 2018 season ranks 20th. A lot of that has to do with context. Genda is an amazing fielder, but NPB’s defensive standards are now remarkably high.

Win shares rates former Marines shortstop Makoto Kosaka as the best to play the position in the past 25 years and he is the only player in the last 50 years to have a season value ranked in the top 10.

For non win shares people, be warned that while win shares does give credit to various performance data, it is heavily weighted toward the context in which those data are compiled. It matters how many games your team wins, how good the team’s fielding is in relation to its batting and pitching, and how good the overall team defensive numbers at each position compare to the league norms. Good teams have more credit to pass around than weak teams and players who perform above the league’s norms will have a larger share of his team’s defensive credit than those who are below average and so on.

I’ve tried to post output from my database here in large files that can easily be read, but I’m not a database person or much of a coder, so that technology escapes me. I hope to remedy that by posting files of the top 20 in each defensive category by position on the data page, at least that way readers can monitor what the different records are.