Koji Uehara has officially retired from professional baseball.
The longtime star reliever announced his decision at a press conference in Tokyo, Japan, on Monday. He'd been pitching for the Yomiuri Giants of Nippon Professional Baseball this season, but hadn't been called up to the first team.
"I want to end my 21-year baseball career today," Uehara said, according to The Japan Times. "There is a part of me that wants to play on, but I decided from the beginning (of the season) that this is my last."
Uehara, 44, began his pro career with the Giants in 1999 before eventually moving to Major League Baseball in 2009 as a member of the Baltimore Orioles. The Orioles used him as a starter that season, but he converted to the bullpen the following year.
The right-hander had a season for the ages in 2013, when he joined the Boston Red Sox en route to the World Series championship. That year, Uehara recorded 21 saves while posting a 1.09 ERA, a 0.57 WHIP and a 12.2 K/9 rate over 74 1/3 innings. He finished seventh in American League Cy Young Award voting.
He was heavily relied upon in the 2013 postseason as well, earning ALCS MVP honors for his performance against the Detroit Tigers after throwing six scoreless innings in five games. He was also on the mound when the Red Sox finished off the St. Louis Cardinals in the World Series.