After playing football with the Denver Broncos, Thornton began training under Brad Rheingans in order to become a wrestler. On May 3, 1991, he debuted in the American Wrestling Association, where he lost to Frank Andersson. That same month, he toured New Japan Pro Wrestling. Having an extensive background in martial arts, Thornton fought in an infamous "Different Style Fight" against Shinya Hashimoto, which he lost in the second round.