India's PV Sindhu stuns world No 1 Tai Tzu-ying at badminton's World Tour Finals

Sindhu sank to her knees at the end of an exhausting 14-21 21-16 21-18 victory over the Taiwanese in 62 enthralling minutes in the southern Chinese city of Guangzhou.

The 23-year-old, a silver medallist at the Rio Olympics in 2016, faces Zhang Beiwen of the United States on Friday looking to make it three wins out of three in Group A of the £1.2m end-of-year showpiece.

"Each point was hard fought," said a relieved Sindhu, ranked sixth in the world.

"There were long rallies with good strokes. She was very deceptive and I had to be ready for her strokes.

"Even though I was trailing in the third game I didn't lose hope and I kept fighting."