Despite being one of the top kickers available in the 2003 NFL Draft, Duval was not drafted into the National Football League, but did sign as an undrafted free agent with the NFL's Jacksonville Jaguars. He was waived by Jacksonville on June 19, 2003 and later signed with the Atlanta Falcons. He was waived by Atlanta on August 29, 2004, and subsequently left the NFL to sign with the Montreal Alouettes of the Canadian Football League. Duval made an immediate impact in the CFL, leading the league in scoring his rookie season (2005) with 191 points and proved to be very reliable kicking field goals. His 2005 CFL highlight came in the 93rd Grey Cup when he made a 27-yard field goal with no time left to force overtime. Continuing his 2005 success, Duval led the league in field goal percentage with 86.4% in 2006 which led to his making the 2006 All Star team. He also finished second in kicking points (201), punting average (45.4 yards) and kickoff average (61.1 yards). Duval's strong play helped Montreal reach the 94th Grey Cup by kicking a game sealing field goal in the Division finals. Unfortunately, his team fell short again despite Duval's 43 yard field goal in the second quarter. On November 7, 2009, he set the record for points in the CFL regular season with 242, again with the Montreal Alouettes.