At just 25 years of age, Duncan has won 7 out of the last 8 New Zealand GC Open Championships, making him one of the top players of NZ. Duncan was also the first winner of the U21 World Championships, and was captain of the NZ team at the World Team Championships held in Johannesburg.
Every time Duncan has entered the World Championships, he has always progressed further than the last, with years placing as 6th overall. Duncan is also on the NZ GC selection panel.