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

Year	League	Team	Name R	G	PO	A	E	DP	Field
2018	PL	Lions	Sosuke Genda	143	271	526	11	112	.986
1963	PL	Hawks	Kenji Koike	147	295	493	23	111	.972
2008	CL	Tigers	Takashi Toritani	144	263	476	15	107	.980
1985	CL	Carp	Yoshihiko Takahashi	130	239	468	16	107	.978
1998	PL	Marines	Makoto Kosaka	123	236	417	16	106	.976
1981	PL	Braves	Keijiro Yumioka	130	210	449	17	104	.975
1964	PL	Hawks	Kenji Koike	149	289	498	36	103	.956
2007	CL	Carp	Eishin Soyogi	135	231	439	13	103	.981
1991	CL	Swallows	Takahiro Ikeyama	132	270	412	4	101	.994
2006	CL	Tigers	Takashi Toritani	146	213	490	21	100	.971
2001	CL	BayStars	Takuro Ishii	140	252	417	12	100	.982
2016	PL	Fighters	Takuya Nakashima	143	219	447	14	100	.979

Top 10 NPB shortstop seasons ranked by total assists

Year	League	Team	Name	G	PO	A	E	DP	Field
2018	PL	Lions	Sosuke Genda	143	271	526	11	112	0.986
1948	1L	Dragons	Kiyoshi Sugiura	137	268	502	45	90	0.945
1954	PL	Buffaloes	Takeshi Suzuki	132	219	501	44	68	0.942
1964	PL	Hawks	Kenji Koike	149	289	498	36	103	0.956
1963	PL	Hawks	Kenji Koike	147	295	493	23	111	0.972
2001	PL	Marines	Makoto Kosaka	140	252	492	16	99	0.979
2006	CL	Tigers	Takashi Toritani	146	213	490	21	100	0.971
2000	PL	Marines	Makoto Kosaka	135	226	489	11	98	0.985
2003	PL	Marines	Makoto Kosaka	134	226	483	8	86	0.989
2017	PL	Lions	Sosuke Genda	143	228	481	21	89	0.971

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.