Opdal was born in Odda, and played for Odda FK until he joined SK Brann in 2000. Opdal made his debut for the first team in the Third Round match of the 2001 Norwegian Football Cup against Ørn-Horten. He made his debut in Tippeligaen in the match against Rosenborg on 27 October 2002. Opdal was reserve to Ivar Rønningen for a couple of seasons, but Opdal made his breakthrough during the 2003 season, when he started some matches in Tippeligaen. Opdal became regular in the starting lineup when Rønningen was sold in the middle of the 2004 season, leaving Opdal with competition from Johan Thorbjørnsen. Opdal became a hero in one of his first starts. In a game in the 2004 Norwegian Football Cup against Bodø/Glimt the score was 3–3 at the end of regular time. In the penalty shootout, Opdal saved a penalty from Aasmund Bjørkan and later scored the winning penalty himself. Brann carried on to win the cup that year.