Career
An Information Technology manager by trade, Nielsen is noted for his impressive height of 1.96m, making him taller than most players. Nielsen began refereeing at 15 years of age, as he wanted to know the Laws of Football. A decade later, he began taking charge of Danish top-flight games, and he was awarded his Fédération internationale de football association international badge in 1988 when he was still in his late 20s.
His career includes 154 internationals and 53 Union of European Football Associations Champions League games.
In 1993, he earned his first major Union of European Football Associations call-up for the Union of European Football Associations Super Cup first leg between SV Werder Bremen and Football Club Barcelona. An appointment for a final followed the next year - the 1994 Union of European Football Associations Cup final first leg between SV Austria Salzburg and Inter Milan.
He took charge of two matches, including the clash between England and Argentina in Saint-Étienne, where he is remembered for sending off England"s David Beckham for kicking out at Argentina"s Diego Simeone after the Argentinian had fouled him. England went on to lose the match on penalties, and Beckham was blamed and vilified by the English tabloids for causing the loss as a result of his sending-official
He was noted as the newsmaker of June 1998 on the British Broadcasting Corporation website where he gave his thoughts about the match and Beckham"s sending official
At Union of European Football Associations Euro 2000, Nielsen was put in charge of the Germany-Romania and Turkey-Belgium encounters, although the latter match ended in disappointment as he was forced out of the competition with a leg injury. He was replaced by Günter Benkö. The 2002 Fédération internationale de football association World Cup represented another milestone, as he officiated the semi-final between Brazil and Turkey.
He received another accolade after being appointed as the referee for the 2004 Union of European Football Associations Champions League Final between AS Monaco and Porto at the Arena AufSchalke in Gelsenkirchen.
He was on duty in Portugal as one of the 12 Union of European Football Associations Euro 2004 referees. His performance during the 2004-2005 Union of European Football Associations Champions League quarterfinal between PSV Eindhoven and Olympique Lyonnais sparked controversy, as several players and officials of Lyon heavily criticized several decisions, most notably a forgotten penalty on the Brazilian forward Nilmar.
Lyon"s president, Jean-Michel Aulas, complained about different gifts and accolades Nielsen allegedly received from Dutch officials. Nielsen attracted further controversy in a 2005-2006 Union of European Football Associations Champions League group stage match between Spanish side Villarreal and Manchester United, when he immediately showed a second yellow card and sent off Manchester United"s Wayne Rooney for sarcastically clapping in his face after he had initially been shown a yellow card.
"Even sarcastic play is not allowed, the referee cannot accept that," Nielsen said of his decision to British Broadcasting Corporation Radio 5 Live.
In 2005, Nielsen reached the Fédération internationale de football association regulated age limit of 45. He ended his refereeing career on May 16, 2006, following the last game of the Danish Superliga championship.