South Korea's top seed Lee Dong-keun cruised into the second round of the Badminton World Federation (BWF) US Open as other contenders tumbled around him in Fullerton.
The 28-year-old, who won a team gold medal at the 2014 Asian Games in Incheon, knocked out China's Zhou Zeqi 21-9, 21-10 at the Californian city's Titan Gym.
Lee, the world number 30, will now play Japan's Koki Watanabe in round two but four of the eight seeds departed the tournament at the first hurdle.
Dutch third seed Mark Caljouw was the highest-ranked casualty as he lost 21-17, 21-11 to Chinese Taipei's Lin Yu-hsien.
There was also an early exit for France's eighth seed Thomas Rouxel who was a handed a tricky draw against China's Youth Olympic Games champion Li Shifeng.
Li, who won the Canadian Open last week, negotiated yesterday's qualifying tournament and the 19-year-old came from behind to win 15-21, 21-18, 21-16.
Another Frenchman had more joy as Lucas Corvée battled back to oust England's fifth seed and former European champion Rajiv Ouseph 16-21, 21-19, 21-18.
Indian sixth seed Parupalli Kashyap, beaten by Shi in the Canadian Open final, lost to his fellow countryman Lakshya Sen 21-11, 21-18.
In the women's draw Canada's top seed Michelle Li eased past American home hope Jennie Gai in round one, 21-9, 21-10.
She will now meet another home player, Crystal Pan, in round two.
Japan's second seed Saena Kawakami was equally comfortable as she defeated Chinese Taipei's Chiang Ying-li 21-13, 21-12.
China's fourth seed Zhang Yiman was the only one of the ranked players to be knocked out as she fell 21-17, 21-18 to South Korea's Sim Yu-jin.
Wang Zhiyi, China's Youth Olympic silver medallist, continued her march from the qualification tournament by beating Mexico's Mariana Ugalde 21-10, 21-8.
South Korean 17-year-old An Se-young, the fifth seed who has won the Canada and New Zealand Opens this year, eased past American Disha Gupta 21-9, 21-8.
Action continues tomorrow, with the finals at the BWF Super 300 World Tour event on Sunday (July 14).