Top-ranked South Korean archer Choi Mi-sun was stunned in the quarterfinals of the individual event at the Rio de Janeiro Olympics on Thursday.

Alejandra Valencia of Mexico upset the world No. 1 by the set score of 6-0 (25-23, 29-26, 29-27) to advance to the semis.

Each set consists of three arrows per archer. A set win is worth two points and a draw is one point. The first to six points wins the match.

Choi shot a disastrous 5 with her first arrow, and hit just one 10. Valencia hit four 10s.

Choi helped South Korea to the team gold medal earlier in the Olympics.

Choi was overcome with emotions after the loss, saying she will remember the Rio Games as a disappointing one, despite her team gold medal.

"I think I got too conscious of the wind and didn't concentrate on my own posture," she said, fighting back tears. "I've prepared so much for the Rio Olympics and it feels very hollow to have it end like this. (Yonhap)