Fields was originally selected by the Chicago White Sox in the first round (18th player chosen overall) of the 2004 First- Year Player Draft. He made his Major League debut with the White Sox in 2006 after being named to the mid- and postseason International League All-Star teams while playing with Charlotte.
During his rookie season with Chicago in 2007, Fields hit 23 home runs and knocked in 67 runs in 100 games and received one third-place vote for A.L. Rookie-of-the-Year. Prior to the 2007 campaign, he was ranked by Baseball America as the No. 2 Prospect and Best Power Hitter in the White Sox organization and the 45th-best prospect overall in baseball.
Primarily a third baseman, Fields has also seen action at second base and in the outfield during his big league career. The right-handed hitter has spent parts of each of the last five seasons in the Majors with the White Sox (2006-09) and Royals (2010) and has produced a .234 average (167-for-713), 34 homers and 107 RBI in 217 games.
With the addition of Fields, the Pirates now have 8 non-roster players scheduled to attend spring training (5 pitchers, 1 catcher and 2 infielders).