 At the start of the 2007–08 season, with Rasmus Marvits having left the club, Petersen became a regular part of the starting 11 in the AC Horsens' first team.After Petersen joined the Danish national league team's 2009 King's Cup campaign, twice playing 90 minutes, Peter Bonde, the assistant manager of Denmark, praised him, and told he had A-national team potential.On January 7, 2016, it was announced, that Petersen had to find a new club when his contract with AaB expired at the end of the season.