After winning a local amateur Toughman competition, Jaco trained for a year to turn pro. Jaco's first high-profile victory came against a young Canadian fighter and future title contender
Donovan Ruddock, whom he beat on April 30, 1985 under controversial circumstances when Ruddock's corner threw in the towel in the eighth round. According to the media, Ruddock later was found to have a respiratory illness that almost ended his career, which may have contributed to breathing problems that caused his corner to stop the fight. Regardless, Jaco won the fight and gained more publicity to further promote himself to fight big time opponents. The victory over Ruddock was the last Jaco would see until 1988 as he was beaten in his next nine fights, seven times by knockout. Among the fighters he took on were contender
José Ribalta, future titleholders
Tony Tucker,
Buster Douglas, and
Mike Tyson, and former champion
Mike Weaver. Jaco's losing streak was finally broken on March 11, 1988, when he knocked out previously unbeaten Zambian Michael Simuwelu in the first round. Again, it would be his last victory for an extended period. Six defeats followed, including fights against future champion
Oliver McCall, an on-the-comeback trail
George Foreman, and
Tommy Morrison. After his loss to Morrison Jaco went unbeaten in his next five fights, winning four times and drawing against former contender
David Bey. After defeating Danny Sutton in the last of those five fights, Jaco never won again. His retirement fight resulted in him getting knocked out by Bey. Former manager Richard Conti said "David fought on guts. That was his biggest strength. He was never the quickest or the strongest fighter. He took a lot of beatings, but he always gave everything he ever had." ==Personal life==