Chinese top seeds Niu Jianfeng and Guo Yue lost 4-2 to compatriots Wang Nan and Zhang Yining in the women's doubles table tennis semi-finals on Thursday.
The two Chinese pairs, seeded one and two, would almost certainly have met in the final had organisers not changed the rules so that teams from the same country were placed in the same half of the draw.
Wang, the Olympic singles and doubles champion, and Zhang will play South Korean third seeds Lee Eun-sil and Seok Eun-mi in the final after they thrashed compatriots Kim Bok-rae and Kim Kyung-ah 4-0 in the other semi-final.
Wang told reporters: "It doesn't matter if I feel happy or not, the only thing that counts is that I want the Chinese to win the gold medal."
In the men's doubles quarter-finals Chinese top seeds Chen Qi and Ma Lin polished off Polish pair Lucjan Blaszczyk and Tomasz Krzeszewski 4-1.
Sweden's Jan-Ove Waldner, the 38-year-old who upset Ma in the singles on Wednesday, was eliminated when he and partner Jorgen Persson lost 4-1 to Danes Michael Maze and Finn Tugwell.
In another surprise Russia's Dimitrij Mazunov and Alexei Smirnov beat South Korean fourth seeds Lee Chul-seung and Ryu Seung-min 4-1 to set up a semi-final with third-seeded Hong Kong pair Ko Lai Chak and Li Ching.
Results: Women's doubles semi-finals:
2 - Nan Wang & Yining Zhang (Chn) beat 1- Yue Guo & Jianfeng Niu (Chn) 11-7, 13-11, 9-11, 13-11, 6-11, 13-11.
3 - Eun Sil Lee & Eun Mi Seok (Kor) beat 9 - Bok Rae Kim & Kyung Ah Kim (Kor) 11-6, 12-10, 11-7, 11-2.
Men's doubles (quarter-finals:
1 - Qi Chen & Lin Ma (Chn) beat 8 - Lucjan Blaszczyk & Tomasz Krzeszewski (Pol) 8-11, 11-6, 11-6, 12-10, 11-7.)
16 - Michael Maze & Finn Tugwell (Den) beat 13 - Jorgen Persson & Jan-Ove Waldner (Swe) 11-5, 8-11, 11-8, 12-10, 12-10.
4 - Chul Seung Lee & Seung Min Ryu (Kor) beat 9 - Dimitrij Mazunov & Alexei Smirnov (Rus) 12-10, 7-11, 9-11, 4-11, 8-11.
3 - Lai Chak Ko & Ching Li (Hkg) beat 7 - Slobodan Grujic & Aleksandar Karakasevic (Ser) 11-6, 10-12, 11-6, 13-11, 11-9.