In the subsequent point, the Indian hit it out to give the title to Beiwen.
However, Mathias and Christinna managed to move to a 19-15 lead before sealing the opening game when Pranaavs return went to net.
The match looked like it was heading towards Zhang as she took a 19-17 lead.
Sindhu continued the momentum shift to level the decider 11-11 after the break.
"I had nothing to lose and pressure was on Sindhu".
Meanwhile, ace Indian shuttler Saina Nehwal will also aim to seal a semi-final spot when she square off with fifth-seed Beiwen Zhang of U.S. in another quarter-final clash later today. In the second game, Ratchanok tried to push Sindhu with some clever placements but Sindhu kept firing smashes to quell the challenge from the Thai. Representing a country without much of a badminton culture - though she still holds a Singapore passport - she did not have a coach till very recently, though he cannot travel to tournaments with her as she can't afford it. But Beiwen fought back to make it 3-3 first and then 4-4.
Zhang capitalised on the opportunity to deny the world No.4 any further leeway, claiming three points in a row to seal the deciding game 22-20.
In the third and last set, the Chinese-American shuttler zipped past Sindhu with some impressively delivered net-shots to put the Rio Olympics silver medallist under pressure. With both players visibly exhausted, the serves changed hand regularly and with it the points too, 15-15.
The second game was a little more closely fought, with Intanon managing to get her game going. But Sindhu again clawed her way back at 19-19 by punishing Zhang for a poor return and pushing the shuttle at the back after leaving her opponent out of position. "Smash, smash, smash", said Yuki, still trying to catch his breath after a 42-stroke rally for the penultimate point in the deciding game.
After the interval, Zhang drew parity at 12-12 following a miscued shot near the net by Sindhu. The fourth-seeded Chinese, who had made it to the final of the All England Open Championships past year, defeated third seed Chou Tien Chen 21-18, 21-14 in 47 minutes.
For 21-year-old Yuqi, it was his first title since French Open victory in October 2016. Gold medals at the Youth Olympics and Junior World Championships attest to his talent, but Shi Yuqi had gone a full year without a title.
Looking ahead to the season, he hoped to build on from here. "I guess it is the best moment of my career", she said.
Men's doubles top seeds Marcus Gideon and Kevin Sanjaya from Indonesia defeated fourth seeds Kim Astrup and Anders Skaarup Rasmussen from Denmark 21-14, 21-16 to retain their title.
Attacking Sindhu holds her own to reach semis even as Nehwal and Kashyap exit India Open. He won 18-21, 21-10, 21-19.