Top women's singles seed and Tokyo Olympic champion Chen Yufei of China suffered a major setback in Bangkok, Thailand on Wednesday, losing her opening match of the Badminton World Federation (BWF) World Tour Finals. 

In a three-set battle, world No. 4 Chen lost 21-9, 14-21, 21-16 to Indonesia's Gregoria Mariska Tunjung, who only made it to the finals following the withdrawal of India's world No. 6 Pusarla V. Sindhu. 

"It was the first match so I was still unfamiliar with the stadium, especially the wind and I had a slow start," said Chen after the match. 

Meanwhile, for her part, world No.18 Tunjung, 23, said: "She didn't settle down well in the first game so I tried to put as much pressure on her as possible. During the match, I tried my best not to think about the result and just gave my all, and I'm happy with the win."

The upset means Chen is facing a daunting challenge to qualify for the semifinals as her two remaining opponents in the group stage are the top two world ranking players – Japan's Akane Yamaguchi and South Korea's An Se-young. 

In the other women's singles group, Chen's teammate He Bingjiao defeated Tai Tzu-ying of Chinese Taipei in straight sets 21-19, 21-19. 

Another setback for China on Wednesday came from the mixed doubles when Tokyo Olympic gold medalists Wang Yi Lyu/Huang Dongping went down against Malaysian duo Tan Kian Meng/Lai Pei Jing 23-21, 14-21, 21-16. Their compatriots Zheng Siwei and Huang Yaqiong, the reigning world champions, strolled past Thom Gicquel/Delphine Delrue of France 21-8, 21-9. 

The only Chinese shuttler in the men's singles Lu Guangzu was no match against world No. 1 Viktor Axelsen of Denmark, losing 21-13, 21-11, but China's men's doubles pair Liu Yuchen/Ou Xuanyi had a good start for the tournament by defeating Kim Astrup/Andres Skaarup Rassmusen of Denmark 21-11, 21-19. 

In women's doubles, the two Chinese pairs were drawn into the same group where world No. 1 Chen Qingchen/Jia Yifan beat Zhang Shuxian/Zheng Yu 21-18, 17-21, 21-14. 

The by-invitation finals feature the top eight players and pairs on the BWF World Tour rankings, with a maximum of two players or pairs per member association eligible. Players in each individual event are drawn into two groups where the top two of each group qualify for the semifinals.

(With input from agencies)