Defending champion PV Sindhu lost her opening match 21-18, 18-21, 8-21 to Japan's Akane Yamaguchi at the year-ending BWF World Tour Finals in Guangzhou, China on Wednesday.
Sindhu squandered an 11-6 lead in the second game against former world no 1 Yamaguchi, who scripted a sensational comeback after losing the first game to claim her third successive win over the Indian.
Sindhu came into her campaign opener with a healthy 10-6 head-to-head record against Yamaguchi but she had lost to the Japanese in the last two meetings this year.
World No. 6 Sindhu will next face China's Chen Yu Fei in her second group A match on Thursday.
The 2019 World Tour Finals are the second edition of the round-robin style season-ender under the BWF World Tour's revamped structure that came into effect last year. It consists of the top eight players/teams across five categories, based on their points accumulated from the year's 37 calendar events.
Sindhu did not finish in the top eight but secured her place in the draw by winning this year's World Championships. Players/teams are divided into two groups, where they play each other once. The top two from each group make the semifinals, with the winner of one group taking on the second-placed player in the other.