Duncan played for Clemson University for a year . He reached the individual finals of the National Collegiate Athletic Association , in which he was subject to Mikael Pernfors . He was then voted into the All-American selection. Towards the end of 1984 he became a professional tennis player. The following year he reached the final of an ATP tournament three times , but lost all three games. 1986 was much worse, his best results were quarter-finals in Bari and Saint-Vincent . Due to injuries he was able to play only a few games in 1987. Since he had slipped on the world rankings, he played on the ATP Challenger Tour ; there he could win the tournaments of Agadir and Casablanca . Between 1988 and 1990 he was another three times in a final on the ATP World Tour. In the course of his career, however, he was never able to win there. He reached his highest ranking in the tennis world rankings in 1985 with position 47 in singles and in 1987 position 182 in doubles.
His best individual result at a Grand Slam tournament was reaching the round of 16 of the French Open in 1989, in which he was defeated by defending champion Mats Wilander .
United States
Madrid
Andreas Maurer
Horacio de la Peña
Bari
Thomas Muster
Magnus Larsson