- Bats Right, Throws Right
- Height 6' 0", Weight 182 lb.
- High School Gifu Tandai Fuzoku High School
Koichiro Sasaki pitched for 20 seasons in Nippon Pro Baseball, making two All-Star teams.
Sasaki signed with the Taiyo Whales initially, going 1-0 with a 5.23 ERA in four outings in 1962. They released him and he signed with the Kintetsu Buffaloes. He had a 4-5, 3.09 record for the Buffaloes in 1963. In 1964, he started 24 games then relieved in 49 more for 73 outings and 227 1/3 IP. He was 10-17 with a 3.13 ERA and 1.08 WHIP that year. He led the Pacific League in games pitched. He fell to 7-20, 3.86 in 1965 and tied Masaaki Koyama for the league lead in losses.
Sasaki improved to 8-12, 2.81 with a .226 opponent average in 1966. He had a 14-10, 3.38 record in 1967, walking only 45 in 218 1/3 innings. He was 11-15 with a 3.47 ERA in 1968, the year he made his first PL All-Star team. He made his other All-Star team in 1969, when his record was 15-7, 2.35 with a 1.03 WHIP. He was in the league's top 10 in ERA for the first time, placing third behind Masaaki Kitaru and Toshihiko Sei.
The Gifu native had his best season at 17-5, 2.05 with a 1.03 WHIP again in 1970, including a ten-game winning streak. On October 6, he threw the 11th perfect game in NPB history, shutting down the Nankai Hawks. Michio Sato edged him by percentage points for the ERA crown. The right-hander led the league with six shutouts. In 1971, he was still productive, but not nearly as sharp at 13-11, 3.19. He was 5th in ERA, between Tamehiro Kaneda and Toshio Kanbe. Two highlights that year were his 100th win (October 4) and 1,000th strikeout (July 4).
Sasaki fell back under .500 with a 10-15, 3.47 campaign in 1972; one positive was that he threw five shutouts to tie Sei and Keishi Suzuki for the league lead. He really struggled in 1973, going 2-9 with a 5.56 ERA and .301 opponent average. Sasaki went 2-1 but with a 6.23 ERA and .324 opponent average in 1974.
Koichiro ended his career with the Hawks. He rebounded to 4-4, 3.60 in 1975, was 2-3 with a 4.31 ERA in 1976 and 4-2 with a save and a 3.47 ERA in 1977. In 1978, Sasaki was 1-5 with two saves and a 3.09 ERA, pitching almost exclusively in relief. He was 3-7 with a save and a 3.48 ERA in 1979 then 3-4 with a 7.98 ERA, 17 HR in 58 2/3 IP and .328 opponent average in 1980. He concluded his career with 13 games in 1981, allowing a .336 average and 5.13 ERA while winning his last decision.
Overall, Sasaki was 132-152 with a 3.39 ERA in 667 NPB games. He allowed 619 walks and 2,479 hits in 2,620 1/3 innings while fanning 1,353. He later was a baseball commentator on TV.
Source: Japan Baseball Daily