A first-half Zlatko Janjic penalty was enough for Duisberg to cause an upset in the DKB-Pokal Cup first round on Friday evening as they beat Nuremberg 1-0.
Nuremberg were playing Bundesliga football last season but were not strong enough to overcome the challenge of their third-tier opponents at the MSV-Arena.
The hosts scored the only goal of the game on 11 minutes as Janjic found the top corner with his spot kick, which he had earned by drawing a foul from Nuremberg defender Niklas Stark.
Janjic could have doubled his side's advantage when he headed Michael Gardawski's cross straight at Raphael Schafer on 34 minutes, and Duisberg did not get another clear-cut chance as Nuremberg pushed for an equaliser.
Peniel Kokou Mlapa dragged an 82nd-minute effort and also headed over in stoppage time, while Duisberg stopper Michael Ratajczak saved well from a 90th-minute Dave Bulthuis header.
Duisberg's progress to the last 16 of the competition came in less spectacular fashion than Bayer Leverkusen's 6-0 victory over third-tier opposition and Chemnitzer FC's penalty-shootout upset of Mainz.