Birmingham (AFP) - Ratchanok Intanon, the former world champion from Thailand who only just won a fitness race to be ready for this week's All-England Open, made a startling recovery to defeat Olympic champion Carolina Marin on Friday.
Marin had not won a Superseries event since her Rio triumph, and although she vowed to rectify that by winning the title this week, she slid from within sight of victory to an improbable 22-20, 13-21, 21-18 defeat.
She was 18-11 up in the final game.
"I was in control of the match at 18-11 but I lost focus," she said. "My opponent rushed me and I can't understand why I lost it."
Ratchanok next plays a surprise semi-finalist, Akane Yamaguchi of Japan, whose 21-23, 21-14, 22-20 victory over the fourth-seeded Sun Yu ended the Chinese bid to regain a women's singles title they have dominated for a large part of two decades.
Earlier Tai Tzu-ying, the top-seed from Chinese Taipei, reached the semi-final with an impressive 21-14, 21-10 win over P.V. Sindhu, the Olympic silver medallist from India.
India's Saina Nehwal was also sent packing, losing 22-20, 22-20 by Sung Ji Hyun of Korea after leading 17-12 in the first game. Sung next plays Tai.