Naomi Osaka wins but there are two huge upsets on Day 4 of 2025 Australian Open

Naomi Osaka looked doomed. She dropped the first set of her second-round match against Karolina Muchova 6-1 and was thoroughly outplayed in nearly every facet of the game. Maybe her return to prominence in 2025 was not quite ready to take place. Then things changed.

The Japanese player continued to hit with power, likely even more in sets two and third, and eventually Muchova wilted. That is no small feat as the Czech can hit people off the court as well. She did so against Osaka in the second round of the 2024 US Open. After the match in Melbourne, Osaka said she reminded herself not to think about what happened in set two and just play freely.

In the end, Osaka won 1-6 6-1 6-3, and she looked every bit a real threat to make a deep run at the 2025 Australian Open, a tournament she has won twice before. While that was some time ago, she is still young enough, and clearly talented enough, to be a dangerous opponent for any player.

Naomi Osaka moves on at the Australian Open but two highly-seeded players bow out

In the third round she will play Belinda Bencic, herself making a comeback after giving birth to a daughter in 2024. This is Bencic's first Grand Slam event back, and she has played well. Osaka should have the edge because of her immense power, though.

Two highly-seeded players were not as fortunate as Osaka, however. 2024 Australian Open finalist Qinwen Zheng surprisingly lost in straight sets to 36-year-old Laura Siegemund. The German was ranked No. 97 entering the match, while Zheng was the five-seed. While Zheng might still win the first major of her career in 2025, she appeared to be far too easily distracted by minor things in the match.

During the second set, she was issued a time warning for taking too long to change her shoes, for instance. This seemingly caused her next service game to not go well. If Zheng wants to be great, she needs to maintain more focus is high-stress matches.

On the men's side, six-seed Casper Ruud lost to 19-year-old Jakub Mensik in four sets. To be fair, Ruud's loss is not overly shocking as he is more of a clay-court specialist and had only made it as far as the fourth round once in Melbourne. Meanwhile, Mensik has the game to be a top-10 player on the ATP consistently over the next decade. The Czech could be a dark horse to win the Australian Open.

More tennis news and analysis: