Hendra Setiawan
In 2006, Koo's coach, Rexy Mainaky, decided to paired him with the hard-hitting left-hander Tan Boon Heong. Together, they won the gold medal at the 2006 Doha Asian Games as an unseeded pair. En route to the finals, they defeated several top pairs including Markis Kido and Hendra Setiawan of Indonesia. They are the youngest ever men's doubles pair to win an Asian Games gold medal at the age of 22 and 19 respectively. 2007 was the best year for Koo and Tan. They won several Superseries tournaments and climbed to the top of world rankings. They also won their first All England Superseries title after beating Chinese pair, Cai Yun and Fu Haifeng in straight games.