Commonwealth Games bronze medallist Richard Vaughan has crashed out at the last-16 stage of the men's badminton.
The 26-year-old Welshman fell 15-9, 15-4 to Korea's Seung Mo Shon.
Vaughan's Athens build-up was hampered by a hip injury and he looked out of touch against the seventh seed, his play at the net letting him down.
Women's doubles pair Ella Tripp and Joanne Wright also suffered a straight set, 40-minute defeat to Dutch pair Mia Audina and Lotte Bruil (15-7, 15-7).
Vaughan's conqueror Mo Shon will now play second favourite Chen Hong, who survived by the skin of his teeth against Malayasian Lee Chong-Wei, eventually winning 15-13, 3-15, 15-12.
With the first-round exit of top seed Lin Dan, Chen is the only Chinese survivor in the last eight.
Ronald Susilo of Singapore, who accounted for Lin, booked his quarter-final slot with a 15-11 15-6 victory over Bjoern Joppien of Germany and looks a potential champion.
Peter Gade of Denmark, who beat India's Nikhil Kanetkar 15-10 15-6, and the talented but unpredictable IndonesianTaufik Hidayat, who ousted third seed Choong Hann Wong of Malaysia 11-15 15-7 15-9, are also potential finalists.
Hidayat, the Asian champion, now meets Gade in the clash of the round on Wednesday, and goes in as the underdog after beating the Dane only once in seven head-to-heads.
China look to hold all the aces in Wednesday's women's semi-finals where only ex-Indonesian Mia Audina, who now plays for the Netherlands, can disturb the might of top three seeds Gong Ruina, Zhou Mi and Zhang Ning.
"
We started really well, but our concentration slipped in the second when we were in a strong position and we came under a lot pressure
"
Fu Haifeng
Meanwhile, in the men's doubles Chinese number two seeds Fu Haifeng and Cai Yun were surprisingly beaten 3-15 15-11 15-18 by Jens Eriksen and Marting Lundgaard.
Fu and Cai took the first game of the quarter-final and were up 11-9 in the second, before the Danish fifth seeds hit back.
At 4-4 in the decider, Eriksen and Lundgaard made a decisive break, taking the next nine points to set up the win.
"We started really well, but our concentration slipped in the second when we were in a strong position and we came under a lot pressure," said Fu.
Eriksen and Lundgaard will play unseeded South Korean's Lee Dong-Soo and Yoo Yong-Sung, who upset Malaysian fourth seeds Choong Tan-Fook and Lee Wan-Wah.