Due to early round exits in 2013 and a four-year title drought, Koo parted with the Badminton Association of Malaysia and became a coach for the Granular Club of Thailand in early 2014. In August that year, Koo returned to play his last tournament with Tan at the 2014 BWF World Championships. Their last match together was in the third round where they lost to a Chinese Taipei pair with a score of 19-21 in the deciding game.
In 2015 Koo Kien Keat and Tan Boon Heong announced that they are coming out of retirement. Koo said that he still has love for badminton and both him and Tan both wanted to play together as a pair again and try to qualify for the 2016 Rio Olympics before they call it quits for good. They are currently sponsored by Seri Mutiara Development Sdn Bhd They have achieved some breakthroughs this year. Winning the Russian Open, Yonex Dutch Open and finishing runners up in the Thailand Open. They have also made it to 2 supersedes quarterfinals in Australia and Korea. The pair have been playing very well and the pair say that they are just enjoying their game playing with no pressure.
Koo Kien Keat moves very fast around the net areas and is adventurous with deceptive shots. He also reacts very well on fast flat exchanges. A favourite formation is when he is on the front court and his partner, the main smasher, attacks from the rear of the court with powerful, left-handed smashes.
Kien Keat and Tan Boon Heong are an explosive and dynamic pair in their game style.
In 2010, they won their first title of the year in their home, Malaysia, as the world number 1 pair. They came in seeded number 1 in the All England but lost in the first round to Denmark former world champions Lars Paaske and Jonas Ramussen.