Hidehiko Koga had a multifaceted career in professional baseball. He played in Nippon Professional Baseball and in the American minor leagues, while later becoming a minor league manager in the United States and a front office worker and coach in Japan.

Prior to playing professionally, Koga attended Kumamoto Kogyo High School and then Kinki University

Kinki University

, or , is a private non-sectarian and coeducational university based in Higashiosaka, Osaka, Japan with campuses in five other locations: Nara, Nara; Ōsakasayama, Osaka; Uchita, Wakayama; Higashihiroshima, Hiroshima; and Iizuka, Fukuoka....

. He then played outfield for the Yomiuri Giants

Yomiuri Giants

The are a professional baseball team based in Bunkyo, Tokyo, Japan. The team competes in the Central League in Nippon Professional Baseball, the top level of professional play in Japan. They play their home games in the Tokyo Dome, opened in 1988. The English-language press occasionally calls the...

 in 1962 and 1963, hitting .182 in 11 at-bats. He played 19 games in Nippon Professional Baseball.

Koga then pitched in the United States in 1966 and 1968. In 1966, he twirled for the Decatur Commodores

Decatur Commodores

The Decatur Commodores were a professional minor league baseball team based in Decatur, Illinois. They played, with sporadic interruptions, from 1900 to 1974 in a variety of minor leagues, but spent the majority of their existence in the Illinois-Indiana-Iowa League , later joining the...

 in the San Francisco Giants

San Francisco Giants

The San Francisco Giants are a Major League Baseball team based in San Francisco, California, playing in the National League West Division....

 organization, going 7-8 with a 3.20 ERA in 31 games (15 starts). In 1968, with the Lodi Crushers

Lodi Crushers

The Lodi Crushers were a minor league baseball team located in Lodi, California. The team played in the California League, and were affiliated with several major league franchises, the longest being the Los Angeles Dodgers. Their home stadium was Tony Zupo Field. Today, the franchise is the...

 in the Chicago Cubs

Chicago Cubs

The Chicago Cubs are a professional baseball team located in Chicago, Illinois. They are members of the Central Division of Major League Baseball's National League. They are one of two Major League clubs based in Chicago . The Cubs are also one of the two remaining charter members of the National...

 system, he went 1-4 with a 4.25 ERA in 26 games (five starts). Overall, Koga went 8-12 with a 3.51 ERA in 59 games (20 starts). He walked 92 batters and allowed 159 hits in 190 innings pitched. At the plate, he hit .288 in 66 at-bats. HE then played in the Global League, which folded after only two months, in 1969.

From 1990 to 1992, he managed the California League

California League

The California League is a Class A Advanced minor league baseball league which operates throughout the state of California. Before 2002, it was classified as a "High-A" league, indicating its status as a Class A league with the highest level of competition within that classification, and the fifth...

's Salinas Spurs

Salinas Spurs

The Salinas Spurs were a California League team that played from 1982 to 1987 and again from 1989 to 1992. Located in Salinas, California, they were affiliated with the Chicago Cubs from 1982 to 1983, the Seattle Mariners from 1984 to 1987, and in 1989 they had a partial working agreement with the...

, finishing with losing records each season.