Hong Kong - Chinese No 1 Wang Qiang was on the brink of the biggest win of her season on Friday when rain abruptly stopped her quarter-final against world No 5 Elina Svitolina.
The 26-year-old was serving for the match at 15-30, 5-2 in the second set - after cruising to a 6-2 victory in the first set - when the heavens opened.
Play was later suspended until Saturday, giving the sixth seed an agonising overnight wait to close out the win.
Svitolina would be Wang's highest-ranked top ten scalp this year.
The current world number 24 grabbed headlines at the French Open with her straight-sets demolition of Venus Williams, offering a hint of what was to come.
She later overcame Karolina Pliskova in both Beijing and Wuhan, but none of the victories was against such a high ranked opponent as Svitolina.
She also beat Caroline Wozniacki in 2013 aged just 21 when the Dane was ranked No 10.
Wang had seemed in complete control during the match, with the under pressure Svitolina committing a string of unforced errors, before the top seeded Ukrainian was saved by the weather.
The eventual winner will play former world No 1 Garbine Muguruza, who fought off a late comeback by Thailand's Luksika Kumkhum to win 6-2, 7-5.
Muguruza, the 2016 French Open and 2017 Wimbledon champion, is keen to finish what has been by her standards a disappointing season on a high.
She has slumped to a world ranking of 13, while her best Grand Slam performance was a semi final at Roland Garros.
The Spaniard was relieved to keep the hard-fought match to just two sets ahead of her Saturday semi.
"It was very competitive," the 25-year-old.
Kumkhum broke her as she served for the match, levelling the scores at 5-5, before Muguruza finally overcame her opponent, who is ranked 105.
"I feel in the second set she was playing so much better - it was a full battle. I think the difference was a couple of points."
Earlier, China's Zhang Shuai looked in ominous form as she swatted aside last year's runner-up Daria Gavrilova in straight sets.
The world number 39 overwhelmed her Australian opponent - who is ranked five places above her - with the power and precision of her ground strokes and ran away with a comfortable 6-1, 6-3 victory after little more than an hour on court.
Zhang, China's number two, will make her debut in the Hong Kong semis Saturday when she takes on Ukrainian teenager Dayana Yastremska.
"The first and second rounds gave me a lot of confidence - that's why today I played really well," the 29-year-old said.
Zhang will be favourite to win against 18-year-old Yastremska, currently ranked 102.
The 2016 Wimbledon girls singles finalist fought back from an early setback to win only her second WTA quarter-final earlier on Friday.
The teen quickly went down 4-0 to outsider Kristina Kucova - the world No 317 who knocked out Jelena Ostapenko in the first round - before recovering to win 7-6 (8/6), 6-2.