Career
He started his football career at Manchester United, but made no appearances and was loaned to Cambridge United on 9 January 1998. The loan was turned into a permanent move in April 1998 for a fee of £20,000. By the end of the 2006/07 season, Duncan had made 328 appearances for United, scoring 11 times.
In May 2007 he was released on a free transfer by the club
In July 2007 he was appointed to a part-time role working on the public relations/commercial side of the club and is responsible for promoting the club in an ambassadorial capacity. He has also signed as a player for Chelmsford City in the Isthmian League.