He has the school record for single game passing touchdowns with 7 against SMU Fields was selected as the 18th overall pick in the first round of the 2004 Major League Baseball draft by the Chicago White Sox.

Prior to the 2006 season, Fields was once again ranked as the fourth-best prospect in the White Sox organization by Baseball America.

Fields ended his first season as a Major Leaguer by hitting a promising .244, 23 home runs, 67 RBI, and an OPS of .788 in 100 games.

However, Crede arrived at camp fully recovered from his injury and White Sox general manager Kenny Williams was said to be unsatisfied with the trade offers.

Fields had a disappointing, injury-riddled season with the Knights, in which he regressed to a .246 batting average, 10 home runs, 35 RBI and .772 OPS in 75 games.

[15] Fields underwent arthroscopic knee surgery at the end of the 2008 season,[16] and was the White Sox's starting third baseman in 2009 until Gordon Beckham was recalled from Triple-A Charlotte on June 4[17] and took the position.

This would later end up being the game-winning home run in Mark Buehrle's perfect game over the Tampa Bay Rays, winning 5–0.

[19] On November 6, 2009, Fields, along with Chris Getz, was traded by the White Sox to the Kansas City Royals in exchange for Mark Teahen.

[21] However, on March 28, he was traded by the Pirates to the Colorado Rockies at the conclusion of spring training for a player to be named later or cash considerations.

[22] He recorded a .365 batting average with 11 home runs and 45 RBI in 50 games with the Triple-A Colorado Springs Sky Sox before being released on June 28, in order to pursue a career in Japan.