Most of the spectators at the Nagpur Divisional Sports Complex had already left by the time 24-year-old Subhankar Dey lost the first game of his quarter-final match against B Sai Praneeth in the senior national badminton championships.

The remaining few had all gathered around the player’s enclosure, jostling for an autograph or selfie with PV Sindhu and K Srikanth, who had won their respective matches.

At the other end of the complex, far away from the spotlight, Dey switched on after that first game and started giving the Singapore Superseries champion a real run for his money. The world No 67 threw the kitchen sink at Sai Praneeth, bringing his best attacking game forward and took the match into a decider.

Some more gripping badminton followed in the third game, even as Sindhu and Co were whisked away by security. The groans of the kids who had not got an autograph, however, were to be drowned by roars from Dey at the other end, as he came back from 9-14 down to level the scores 18-18.

That was soon to become 20-20, with Sai Praneeth refusing to give in. Dey had also started getting cramps and was barely able to walk straight. He had played another three-gamer earlier in the day against Daniel Farid, which also clocked over an hour. On Sunday, too, he had engaged Kartikey Gulshan Kumar in a 53-minute three-game match.

However, the 24-year-old dug in to scrape up the last bit of juice left in him as he won two points in a row to take the third 22-20. “I am very happy that I could pull this off,” said the White Peacock Academy trainee, who also plays for a club in Denmark. “I had played him five times before and though some of the matches were close, I never defeated him.

Asked how he turned things around, Dey said, “After losing the first game, I told myself to concentrate on just the next point and work hard. He was fresh [after getting a direct entry into the pre-quarterfinals] while I was playing my fifth match and was cramping. But I kept my focus.

“It’s a challenge for anyone who is out of the national camp to beat the top players since we don’t have the quality of sparring and the tournament exposure they get. That is why I also play in Denmark,” he added.

In the semi-final, Dey will face world No 11 HS Prannoy, who beat P Kashyap 22-20, 21-19 in an equally exciting match. In the other half of the men’s singles draw, world No 2 K Srikanth also reached the semi-finals after beating Shubham Prajapati 21-17, 23-21.

Srikanth will take on the previous edition’s finalist, 16-year-old Lakshya Sen, who received a walkover after leading Ajay Jayaram 15-10. The world No 22 retired with a hamstring injury.

On the women’s side, PV Sindhu and Saina Nehwal both won their quarter-final matches comfortably against Shreyanshi Pardeshi and Aakarshi Kashyap. They were joined in the semi-finals by 20-year-old Ruthvika Shivani Gadde and 19-year-old Anura Prabhudesai.

Corrections and clarifications: An earlier version of this story mentioned that Saili Rane had reached the women’s singles semi-finals. This has been corrected to reflect Anura Prabhudesai reaching the semis.