Koji Mitsui (三井 浩二)
- Bats Left, Throws Left
- Height 6' 0", Weight 190 lb.
- High School Hokkaido Ashoro High School
Koji Mitsui has pitched 8 years in Nippon Pro Baseball (through 2008).
Mitsui was picked in the 4th round of the 1991 draft but opted not to sign. He pitched for Nippon Steel for most of the decade. In 2000, the Seibu Lions took him in the 2nd round. He debuted in 2001, going 3-3 with a 5.22 ERA as a swingman. In 2002, he improved to 10-2, 3.15 in 16 starts and 25 relief appearances. He was 5th in the Pacific League in ERA behind Masahiko Kaneda, Dae-sung Koo, Nate Minchey and Kenichi Wakatabe. He made the PL All-Star team. Mitsui had a 3.18 ERA in 3 games in the 2002 Japan Series.
In 2003, the left-hander was 11-5 with a 5.22 ERA. He was second on Seibu in wins, behind Daisuke Matsuzaka. In 2004, Mitsui was limited to 9 games, with a 7.69 ERA and 67 hits in 45 2/3 IP. He was 2-3. He allowed one run in two innings in the 2004 Japan Series.
Koji moved to relief in 2005and was 1-2 with a 4.95 ERA. The next year, Mitsui was 4-1 with a save in 45 games; he had a 1.73 ERA, best on the club. He pitched in the MLB-NPB All-Star Series that winter. In 2007, he remained effective with a 4-2, 2.22 record in 47 outings. Only Eiji Shotsu had a lower ERA on the Lions.
Mitsui struggled in 2008 as the veteran faded to 1-1, 7.50 and allowed 33 hits in 24 innings. He allowed one run in 1 1/3 IP in the 2008 Japan Series, which Seibu won. Mitsui requested to be posted for MLB teams following the season and Seibu complied, but no club showed no interest considering Mitsui's 2008 campaign. Mitsui was posted again the same off-season and again drew no takers.