Career
He pitched in Major League Baseball from 1998 to 2002. Yoshii played in the Koshien high school baseball tournament twice and joined the Kintetsu Buffaloes as the second round pick in the 1983 draft after graduating from the same elementary, middle, and high schools as former Seibu Lions manager, Osamu Higashio. In 1993, he became a starter.
In the 1997 off-season, he became a free agent and signed with the New York Mets.
He was traded to the Colorado Rockies in 2000 and the Montreal Expos in 2001. He had surgery on his left shoulder in September 2002.
In 2003, Yoshii returned to Japan, joining the Orix BlueWave. He was the team"s opening-day starter that year but had surgery on his left ankle in August.
He ended the season with only two wins.
He played in only three games in 2004 and was cut from the team at the end of the year. On April 1, 2007, he gave up two grand slams in one inning against the Rakuten Eagles, but the third baseman, Greg LaRocca, had committed an error before loading the bases, giving Yoshii the irregular record of 8 runs given up, but 0 earned runs. He continued to pitch during the season as a starter but was demoted to relief duty by manager Terry Collins after several poor performances.
Yoshii requested to be traded to another team where he could continue to start and was sent to the Chiba Lotte Marines on June 28 in exchange for an outfielder.
His pitching continued to decline, and he ended the season with a 1–9 record before being demoted to the minors. He was released by the Marines on November 13, and announced his retirement to become a pitching coach for the Hokkaido Nippon-Ham Fighters under manager Masataka Nashida.