At quarter past midnight, Carla Suarez Navarro won her first game of her quarter-final against Caroline Wozniacki, and it was in the second set.
The unseeded Spaniard was bagel-ed in the first, in which, despite the long and testing rallies, she could only conjure up one break point and failed to convert.
Wozniacki was on song, striking the ball sweetly and oozing confidence as she retrieved impossible balls and piled on the pressure to take the opener to love.
I was disappointed after I had my chance to win in the second set, But I'm proud to have stayed cool and close it out in the third. Caroline Wozniacki
The World No 2 was playing with precision, a woman on a mission, but the canny Suarez Navarro is a fighter, renowned for her three-set victories, and she not only held her next service game but broke the Dane for 3-2, signalling a sea-change.
The Spaniard had won three three-setters in this Australian Open alone and she was ever-so-slowly dismantling Wozniacki’s forehand and sowing the seeds of doubts in the Dane’s head as she went up 4-2.
Using her fine, single-handed backhand to open up the court to great effect, Suarez Navarro pushed home her advantage and had the Dane shaking her head in dismay.
The tables were turning after an astonishing rally, as the Spaniard pulled up a break point, which Wozniacki saved with an ace, but the dogged Dane held on to keep in touch and, in the very next game, she managed to break to level at 4 games all.
The Dane held to love and got to match point at 30-40 in the next but could not find the court with her backhand and Suarez Navarro evened up at 5-5, as the players headed into the tiebreak at 6-6.
Two fine backhand winners off the Spaniard’s racket took her to 3-1 in the breaker as she continued to test the Wozniacki forehand and, although she was levelled again at 3 points all, Suarez Navarro pushed her opponent into errors and won the next four points to force the match into a decider.
“She improved and made me step behind the baseline,” said Wozniacki later. “That made the difference.”
The Spaniard first reached the quarter-final stage of the Australian Open back in 2009, and was two years removed from her last Grand Slam quarter-final, also at Melbourne Park, and her peak ranking of No 6.
Both she and Wozniacki were lucky to be alive at this year’s tournament, the Dane having survived a massive scare, down 1-5 and match points in the third set, against Jana Fett in round two, while Suarez Navarro trailed Anett Kontaveit 6-4 4-1 in the last 16.
Yet both escaped, and were playing with the freedom that comes with a second chance.
Wozniacki headed off for a bathroom break and when play resumed, she looked to have rekindled her energy as the clock headed past 1am early on Wednesday morning.
She quickly regrouped, cranked up the aggression and broke serve in the third game.
It was that aggression that helped deliver her a second service break and a 5-2 lead, an advantage she wouldn’t let slip this time around.
Suarez Navarro sprayed a backhand wide in the eighth game to deliver Wozniacki three more match points on her own serve, forty minutes after squandering her first.
She netted a backhand at 40-0 but forced Suarez Navarro to hit long on the next to secure her place in the semi-finals, 6-0 6-7(3) 6-2, after two hours and eleven minutes, the clock around 1.40am, in front of a remarkably large crowd.
“I knew it was going to be tough against her because in the first set a lot of games were very close,” said the Dane, who is into a second semi-final at Melbourne Park, after losing her first against China’s Li Na back in 2011.
“I was disappointed after I had my chance to win in the second set,” she added. “But I’m proud to have stayed cool and close it out in the third.
“I stepped a little closer to the baseline in the third set, and it felt like I had a little bit more energy left than she did.”
The win keeps the Dane, who can return to the No 1 ranking with her first Grand Slam singles title, on track and, for a place in Saturday’s final, Wozniacki will next meet unseeded Belgian Elise Mertens on Thursday, who accounted for No 4 seed Elina Svitolina in straight sets.
Mertens may be the surprise contender and Belgian tennis might have expected a longer wait for a player to match the achievements of the recently-retired Kim Clijsters and Justine Henin, but she rocketed up the rankings to World No 37 last year.
She saw off Svitolina, who was struggling with a hip injury and was no match for the 22-year-old, winning 6-4 6-0.
Mertens, who trains at Clijsters’ academy in the former World No 1’s home town of Bree, is through to the last four in her debut at the year’s opening Grand Slam event.
Twelve months ago Mertens was not ranked high enough to earn a place in the main draw here and, before she started here last week, she had never gone beyond the third round at a Grand Slam event.
“I’m without words, I don’t know what to say,” Mertens said after winning in just 73 minutes.
“I’ve got nothing to lose, that’s for sure. I have no points to defend. I guess I’m a bit, well, the underdog, as today. But I’m ready for it. I mean, I have a lot of energy left. Mentally, physically good. I’m just going to give it all and see where it ends.”
Mertens’ run is testament to the unpredictability and newfound depth in the women’s game, which has seen newcomers such as Jelena Ostapenko and Sloane Stephens come out of nowhere to win majors in the last year.
First-time semi-finalists have also broken through in 19 of the last 20 majors and Mertens said seeing this has helped her believe that she, too, could contend for a Grand Slam title.
Wozniacki, when asked of Mertens, said: “She’s had an amazing start to the year, I think she’s undefeated.
“It’s going to be a tough one, but I’m excited for it. Another semi-final here – that’s exciting.” she added, with her beaming smile.