There was an interesting post on Twitter Saturday, which just begged for verification. It questioned whether Munetaka Murakami should be considered Japan’s best young home run hitter ever, since the conditions in which the Swallows star has hit his home runs are quite different from those faced by Sadaharu Oh and Hideki Matsui.
Conditions are always in flux, offhand I would agree with this post about Oh, the early part of Matsui’s career was a fairly normal era for home run production. The perception that Matsui hit in a “mini dead-ball era” is created by the switch to Mizuno’s rabbit ball by the Giants, Dragons and BayStars toward the end of his time in Japan.
The same thing probably led Robert Whiting to recently declare Wladimir Balentien’s 60 home runs to have taken place with a lively ball in place. The ball wasn’t particularly lively that year, but it was normal compared to the soft ball used the previous two seasons.
Let’s say we measure the home run norms in each year’s Central League by getting the average number of home runs per at-bat by every player with 300-plus plate appearances, and the standard deviation for that group of players and measure how much better these three hitters were at every year in their young careers with 300-plus plate appearances.
Sadaharu Oh
| Year | Age | HR per AB | SDs above mean |
|---|---|---|---|
| 1960 | 19.6 | 0.040 | +1.03 |
| 1961 | 20.6 | 0.033 | +0.33 |
| 1962 | 21.6 | 0.077 | +3.36 |
| 1963 | 22.6 | 0.083 | +2.74 |
| 1964 | 23.6 | 0.117 | +3.95 |
Hideki Matsui
| Year | Age | HR per AB | SDs above mean |
|---|---|---|---|
| 1994 | 19.6 | 0.040 | +0.48 |
| 1995 | 20.6 | 0.044 | +0.39 |
| 1996 | 21.6 | 0.078 | +1.96 |
| 1997 | 22.6 | 0.076 | +2.07 |
| 1998 | 23.6 | 0.070 | +2.21 |
Munetaka Murakami
| Year | Age | HR per AB | SDs above mean |
|---|---|---|---|
| 2019 | 18.9 | 0.070 | +1.53 |
| 2020 | 19.9 | 0.066 | +1.67 |
| 2021 | 20.9 | 0.078 | +1.95 |
| 2022 | 21.9 | 0.115 | +3.64 |
The league contexts
As I expected, the league home run contexts for regular hitters in the early part of Matsui’s career were not that different from the context Murakami has batted in. The Central League’s 2020 and 2021 seasons were relatively home run-rich environments, but 2022 would have meshed nicely with much of Oh’s early career.
What about their parks?
Murakami plays in Jingu Stadium, a park that greatly increases home run production, but it hasn’t really helped him much. In his career, he’s hit home runs in 8.3 percent of his visiting at-bats and 8.2 percent of his home at-bats.
I don’t have Oh’s and Matsui’s home-visitor splits handy, but I do have their team’s home run adjustments — the degree to which season home run totals for their teams were increased or decreased by the parks they played in.
OK. Let’s assume that Murakami, Oh, and Matsui benefitted or were handicapped by their parks like ordinary hitters. Here they are compared by how many standard deviations their park-adjusted home run rates are above their league averages for regular position players, and I’m going to add one player @GaijinBaseball neglected to mention, Kazuhiro Kiyohara.
The Lions slugger played in a tough home run park but in a home run hitters’ league and was a mile ahead of the competition as a teenager.
Oh became Oh as a 21-year-old. On the verge of professional extinction, he overslept for a day game and fearing he had nothing to lose, broke out the flamingo stance he’d been honing in private on a rainy day at Kawasaki Stadium and turned his career around. Murakami is not quite to the point where Oh was before his monster 1964 season.
| Age | Oh | Kiyohara | Matsui | Murakami |
|---|---|---|---|---|
| 18 | 1.74 | |||
| 19 | 1.04 | 2.06 | 1.08 | |
| 20 | 0.86 | 1.49 | 0.48 | 1.11 |
| 21 | 3.56 | 1.69 | 0.55 | 1.44 |
| 22 | 3.15 | 2.20 | 1.98 | 2.93 |
