Career
He played 32 matches and scored three goals for Norway. Nilsen played for the Norwegian clubs Tromsø, Viking, Molde and Bryne, and spent time abroad at 1. Football Club Köln,, Tottenham Hotspur and Grazer Alaska. He has later worked as assistant coach at Viking.
His career began in Tromsø, but it was after he moved on to Viking that he became established, winning the Norwegian Premier League in 1991.
He was loaned to 1. Football Club Köln, and was put up for sale towards the end of the 1993 season. Having already signed Norwegian team-mate Jostein Flo, boss Dave Bassett added Nilsen in November 1993 for the fee of £500,000, beating Aberdeen to his signature.
Nilsen joined as the club fought unsuccessfully against relegation from the Premier League, and was a regular at left-back. A popular figure at Bramall Lane, Nilsen played six seasons under five different managers, with a number of games at centre-back - particularly after United switched to a wing-back formation in 1997/98.
Never scoring for the Blades, and with Gareth Taylor having missed the first United penalty, Nilsen stepped up to convert the 2nd - powering the ball past Steve Ogrizovic to put the Blades 1-0 up.
After making just three appearances at Spurs, Nilsen had a brief spell at Grazer Alaska before he returned home to play for Molde and Bryne. He left Bryne in 2003, but continued his career in the Norwegian third division with Stavanger IF.
Nilsen represented Norway at youth international level and played for the under-20 team in the 1989 Fédération internationale de football association World Youth Championship. He played 19 matches and scored two goals for Norway U21.
Nilsen made his debut for the senior team in the friendly match against Cameroon on 31 October 1990.
He played his last match for Norway against Sweden on 4 February 2000. Nilsen was capped a total of 32 times, and scored three goals.
In 2006, he retired and took over as head coach for Stavanger IF, guiding the club to promotion to the second division. At the end of the season, Nilsen left the club to take up the assistant coach position at the Norwegian Premier League side Viking.
After manager Uwe Rösler left in November 2009 he was briefly caretaker manager.
He was downsized from his assistant job after the 2010 season. In 2014 he succeeded Odd-Karl Stangnes as manager of IF Fløya"s women"s team, combined with a teaching job at the Norwegian College of Elite Sports in Tromsø.