Career
His position on the field was usually striker, although he also could play as midfielder. Nielsen played 28 matches for Denmark, scoring 7 goals. He made his début against Scotland in a 1–0 loss.
Nielsen started playing football with Brederød IF. He made his a-team début with Bachelor of Arts. In 1971, he left Denmark for Belgium.
His Belgian career took off immediately, with a hat trick in a cup match against Saskatchewan Gullegem. One season later, fellow Danishman Morten Olsen became Nielsen"s teammate.
In 1974, Nielsen went to RWDM. The team became national champions that season. Just like with Cercle, Nielsen would also stay three seasons for the Brussels team RWDM, as he went to their main rivals Anderlecht.
This was also his last season in Belgium.
Nielsen ended his career with French side AS Saint-Étienne. After retiring as a player he worked as a scout for Chelsea F.C. in Denmark. He managed Greve Fodbold from March 2012 until October 2012.