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The Australian Open saw second-round action commence on Day 4 (Wednesday), but for the likes of Sebastian Korda and Felix Auger-Aliassime, it was the end of the road at the season's opening Slam as both men fell prey to upsets.
The two, however, were not alone as plenty of underdogs had reasons to smile on a rain-interrupted day of action at Melbourne Park.
There were some big upsets on both the men's and women's side of things, including the exits of multiple Top-10 stars. Here, we take you through the five most shocking results to have unfolded on Day 4 of the 2025 Australian Open:
#5 Naomi Osaka def. Karolina Muchova
Naomi Osaka is a two-time former Australian Open so a win over Karolina Muchova may not count as much of an upset. That said, the two had come into the tournament under wildly different circumstances.
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Osaka has been finding her way back into form since her return from maternity leave a couple of years ago, while Muchova has found herself playing some of her best tennis in the period. The Czech too had an injury scare derail her progress in 2024 but she was the seeded name coming into the contest.
The Czech's variety was proving too much for Osaka early in the contest, but the former winner turned the match around with her big hitting. She ended the match with 33 winners compared to Muchova's 27 unforced errors and a scoreline reading 1-6, 6-1, 6-3 in her favor. She takes on another returning mother Belinda Bencic, next.
#4 Alejandro Davidovich Fokina def Felix Auger-Aliassime
Alejandro Davidovich Fokina is no stranger to upsets. He has the scalps of Novak Djokovic, Casper Ruud, Holger Rune, and Hubert Hurkacz to boast of. Recently he added another big name, Felix Auger-Aliassime, to that list.
The second-round Australian Open encounter saw an intense battle for the opening couple of sets. It was, however, the Canadian who took the lead by edging both in tiebreakers. Rain delays affected the match like many others on the outside court and momentum swayed from one way to the other.
Fokina took firm control of the match at the beginning of the third set and scripted a memorable comeback to overturn the two-set advantage. He prevailed 6- 7(7), 6-7(5), 6-4, 6-1, 6-3. Jakub Mensik lies in wait for the Spaniard.
#3 Aleksandar Vukic def. Sebastian Korda
Aleksandar Vukic only had one main draw match win in his last six appearances at the Australian Open. He has already surpassed that number and did it in style by taking out the big-hitting Sebastian Korda in the second round.
The Aussie matched his opponent's firepower toe-to-toe and even fired 17 aces (just four shy of his more fancied opponent) to notch up a famous five-set win.
Korda overcame a slow start to take a two-sets-to-one lead but the packed home crowd at the Show Court Arena lifted Vukic, who came back to take the match in five sets 6-4, 3-6, 2-6, 6-3, 7-5. He will now lock horns with another seed, Jack Draper.
#2 Jakub Mensik def. Casper Ruud
A day after Andrey Rublev's shocking exit, another top-10 men's singles seed was shown the door at the tournament on Wednesday. The upset came at the hands of the young Jakub Mensik, who took out Casper Ruud in a late-night thriller.
Mensik, the 2022 Australian Open boys' singles finalist, has been in good form of late. He brought some of the same explosive tennis that has seen him start the season with back-to-back quarterfinals at Brisbane and Auckland to his match against Ruud. He thundered down 22 aces and created 16 break chances, taking five of them.
Ruud, meanwhile, found himself playing on the back foot and could only manage a solitary break of serve. He eventually succumbed in four sets 6-2, 3-6, 6-1, 6-4. Mensik's reward is a third-round date with Alejandro Davidovich Fokina.
#1 Laura Siegemund def. 2024 Australian Open finalist Zheng Qinwen
The upset of the day went the way of Laura Seigemund, the seasoned German who took out last year's women's singles finalist and World No. 5 Zheng Qinwen at the John Cain Arena.
Playing in her eighth Australian Open, Siegemund conjured up all her experience and variety to bamboozle her opponent into submission. She mixed in slices, drop shots, and net approaches to keep Zheng on her toes. The Chinese player, who was playing just her second match of the season, often found herself at a loss for answers as her powerful groundstrokes kept failing to deter an energized Siegemund.
The opening set proved to be pivotal as the German edged her opponent to take it to the tiebreaker before a decisive break advantage in the second set saw her close out an 11th career top-10 win. Siegemund takes on Anastasia Pavlyuchenkova next.
