The world number five defeated Tine Baun of Denmark (world number seven) 21-15, 22-20 to become the first player from India to reach the last four stage of the Olympics.
It was a superb performance from the 22-year-old Hyderabadi on Court 2 of the Wembley Arena. After pocketing the first game at 21-15 in 16 minutes, it was not an easy task in the second as the Dane rallied.
"It's a dream come true for me. It was one of my dreams to play in the Olympic semifinals. Last time in the quarterfinals (Beijing), I was 11-3 up (against Maria Kristin Yulianti) and still lost. I still can't forget that," Saina said after the match.
Saina was pushed to the brink when Baun was leading the second game 20-17 with three game points to take the match into the decider. But, Saina excelled under pressure to save those three game points and win five straight points to wrap the contest 22-20 in 39 minutes.
Saina won 23 points with serve and 20 without serve. She won four points without change of service in the first game and followed that with five in the second. Her biggest leads were eight and three points in first and second games, respectively.
It is for the first time that an Indian player will feature in the semi-finals of Olympics badminton. The last female player was Saina herself, in Beijing 2008, that was only till the quarter-finals. She has now put that disappointment of last eight exit in China to move one step closer to a medal.
Next, she will be up against China's world number one Wang Yihan. Saina will have yet another tough day at office as she has never beaten Wang Yihan in five previous clashes.
Saina is the lone Indian in the semi-finals with the other three slots occupied by the Chinese. One win will ensure Saina a medal but a loss will see her featuring in the play-off match for bronze medal.
Now, let Saina and the whole of India celebrate this huge win. And come Friday, think of the Chinese.
Quarterfinals Results (Women's singles)
Saina Nehwal (India) beat Tine Baun (Denmark) 21-15, 22-20
Wang Yihan (China) beat Cheng Shao-chieh (Taipei) 21-14, 21-11
Li Xuerui (China) beat Yip Pui-yin (Hong Kong) 21-12, 22-20
Wang Xin (China) beat Ratchanok Intanon (Thailand) 17-21, 21-18, 21-14.
Wang Xin and Wang Yihan have advanced to semi-finals of women's singles. So, it is two Chinese in the last four stage. Xin came back from a game down to beat Thailand's Ratchanok Intanon 17-21, 21-18, 21-14 in 64 minutes.
Yihan, the world number one, beat Shao Chieh Cheng 21-14, 21-11 in 40 minutes. If Saina wins, she will face Yihan in semis.
Saina's match was scheduled to start at 6.32 PM IST but has been delayed as there is another quarter-final still going on (Wang Xin, China Vs Ratchanok Intanon, Thailand). The score is 1-1 between Xin and Intanon. It is now time for the decider. After the completion of this match, Saina will be in action.
Saina (fourth seed) is up against Denmark's Tine Baun (fifth seed) in the women's singles quarter-finals. The world number five Indian had reached last eight stage in last Olympics (Beijing 2008) and will be hoping to progress further this time.
No Indian has made it to the semi-finals of badminton and Saina is on the verge of making history.
Saina, the Hyderabadi girl, and Baun have previously met six times and the score stands at 3-3. Baun is world number seven.
"This is not big news (reaching quarter-finals) as I was here last time too (Beijing 2008). I want to do well and reach the semi-finals," Saina had said.
The 22-year-old Saina has won three titles this year. Her opponent is a former All England Open champion and is 33-years-old.
Later in the day, another Indian, P Kashyap will be battling world number two Lee Chong Wei of Malaysia in the men's singles quarter-finals. The match will start at 9.32 PM IST.
Kashyap is the first Indian male player to feature in quarter-finals of Olympics.