Duback grew up in the San Diego, California area where he played for the powerhouse San Diego Nomads youth club. After graduating from high school, Duback attended Yale University where he played on the men’s soccer team in 1982. In 1983, he was the starting goalkeep for the U.S. U-20 national team as it qualified for the 1983 FIFA World Youth Championship in Mexico. He played all three games in the tournament, gaining a single win and single shutout. He retunred to Yale the next season and remained there through 1986. He holds several Yale records, including season GAA (.31 in 1986) and career GAA (.82) . He also hold the school’s record for season shutouts (11) and career shutouts (25). He was named a first team All American goalkeeper in 1984 and 1986. He topped this with garnering the ISAA Goalkeeper of the Year in 1986.
In 1987, he earned his first cap with the national team becoming only one of four national team goalkeepers to earn a shutout in their debut game. Previous to this game, David Vanole had been the keeper of choice through 1986 and 1987. In 1988, the national team began searching for another keeper and Duback was in the mix. However, by 1989, Vanole had staged a resurgance and Tony Meola was entering the goalkeeping scene, which he would dominate through 1994. This led to Duback earning only three more caps, despite his excellent start with the national team. In his for games, he earned only one victory and two shutouts. Duback was also a member of the 1988 U.S. Olympic team which went 0-1-2 at the games.
In 1988, Duback played with the Boston Bolts of the American Soccer League (ASL). In 1993, he was on the roster of the Tampa Bay Rowdies of the American Soccer League which had been created in 1990 by the merger of the WSA and ASL. However, he played in only two games that season as he backed up starter Bill Andracki.
On June 6, 1995, Duback signed with Major League Soccer as that league began preparations to begin its first season in 1996. The league listed him as being with the Charlotte Eagles of the USISL. However, he never signed with any MLS team.
He currently runs goalkeeper camps and markets a goalkeeper video. He served as a volunteer coach at his children's school, Woodlawn of Davidson, North Carolina, during the 2004-2005 season.