After beginning his pro career in 1988 with the Ottawa Intrepid of the Canadian Soccer League. He then joined the Montreal Impact in 1993 and was part of the team’s starting eleven when the Impact beat the Colorado Foxes 1-0 in the playoff final and won the 1994 league championship. He also helped Montreal win the regular-season titles in 1995, 1996, and 1997. In 1995 Barker won the Giuseppe Saputo Trophy and was picked on the league’s first all-star team in 1995. In 1999 Barker was transferred to Impact rivals the Toronto Lynx where he gave new impetus to his career when he moved from the forward position to that of defender.
He left the Lynx in 2001 to join the Impact again where he helped the team win their second League Championship in 2004 against the Seattle Sounders.
He retired as a player following the 2004 season, was third in Impact history for games played (190), as well as second for goals scored (34).
He was assistant coach with the Impact in 2005, helping the team win the regular-season title. He is now the Director of the Impact’s Réno-Dépôt Soccer Schools and the club’s Head of Youth Development.