With a six-point gap, it seemed easy for Sindhu. But Saina, the fighter and the determined competitor, tried to carve out a fierce comeback. However Sindhu held on to her advantage to clinch the first game 21-16.
Even though she lost the first game, Saina's late charge gave her some momentum that she carried into the second game. Her bodyline shots created trouble for Sindhu again.
Moreover, Saina showed her experience as she dictated the pace of the game. She got a 12-7 crucial lead. Having put a lot of energy and power to be in the lead, Saina looked a bit tired, letting Sindhu to come back.
Sindhu, six years younger than Saina, is at her peak and didn't hesitate playing long rallies. She was aided by Saina's tiredness as the latter placed a couple of shots wide and long. Sindhu also snatched a couple of points by smashing cross-court to the left of Saina, who couldn't reply. At the 19-point mark, Sindhu equalised and then Saina played another successful bodyline stroke to be one point away from taking the tie to the third game. But a ruthless Sindhu fought back to be 20-all.
Then, Saina made her first service error at this critical juncture. Sindhu made the most of it. She followed it up with another powerful stroke and the game was over, match sealed.
With this win, double World Championship bronze medallist Sindhu equalised 1-1 in head-to-head record against Saina.
"I felt no pressure even when she was ahead in the second game. I had confidence in myself. When it was 20-20 in the second, it was anybody's game. But I believe in myself and was confident I could turn it around," Sindhu said later.
In the semi-final, Sindhu will face South Korean second seed Sung ji Hyun, who defeated former world champion Ratchanok Intanon of Thailand 21-16, 22-20. The other semi-final will be fought between top seed and 2016 Olympic champion Carolina Marin and Japanese fourth seed Akane Yamaguchi.
Spaniard Marin won against Japanese Minatsu Mitani 21-10, 20-22, 21-14 to set-up a clash against another Japanese. Yamaguchi got the better of compatriot seventh seed Nozomi Okuhara 21-13, 11-21, 21-18.
Meanwhile, men's singles shuttler Sameer Verma's campaign ended with a fighting 22-24, 19-21 defeat to Denmark's Anders Antonsen in 53 minutes. Antonsen will meet Chinese Chou Tien Chen in a semi-final. The other semi-final will witness a battle between Danish third seed Viktor Axelsen and Hong Kong's N.G. Ka Long Angus.