Fields started boxing in 2003 and became the 2005 and 2006 National Golden Gloves Heavyweight champion.
Fields turned pro in 2006 and won his first six fights, five by knockout, before knocking out Mexican 2004 Olympian Ramiro Reducindo on July 27, 2007, in Corona, California in the first round.
On January 18, 2008, Fields defeated former IBF cruiserweight champion Kelvin Davis by technical knockout at 55 seconds of the first round.
In June 2007, Davis had broken his back in two places while training in Australia and was winless in his last eight bouts of a futile comeback attempt, getting knocked out four times after the broken back including the Fields bout.
Fields fought Jeff Yeoman in Oklahoma City on February 11, 2010, and won the fight by technical knockout in the 3rd round.