In 2005, at the Valencia tournament, Dupuis became the first French player to defeat Novak Djokovic. In 2006 he tested positive for the banned drug Salbutamol and was suspended for two and a half months.
Dupuis's victory over Djokovic in 2005 marked a significant moment in his career as the first French player to achieve this feat. However, his success was overshadowed by a doping violation in 2006, leading to a suspension for two and a half months due to testing positive for Salbutamol.