Battle-tested Karolina Muchova powers past Kostyuk's challenge at the US Open

Karolina Muchova booked her place in the US Open quarterfinals after defeating Croatia's Marta Kostyuk 6-3, 6-7(0), 6-3 in a battle of nearly three hours at Flushing Meadows. The 29-year-old Czech is once again having a remarkable campaign in New York, where she has already reached the semifinals in the last two editions.

It's not surprising to see Muchova at this stage. She is a player who has often made headlines with her talent, but injuries have plagued her, preventing her from finding consistency during a full season. Despite a challenging 2025 filled with injuries, the world No. 13 returns to her 7th quarterfinal in a Grand Slam main draw and will face the 4-time major champion Naomi Osaka.

Muchova started the match quickly, taking an early break and holding her first service game without issues to go up 3-0. Kostyuk managed to catch up, improving her statistics on both her first and second serves. Both players won more than 70% of points on their first serve.

The differences in the set were minimal, and what ultimately gave Muchova the advantage were the key moments. She secured a break on two opportunities, while Kostyuk squandered all three of her break points throughout the set. The Czech player took the lead, winning the first set 6-3 after a tight final game where Kostyuk fought to stay alive but couldn't.

In the second set, it was the Croatian who took the lead first. She had already warned with several break points in the first set, and at the start of the second, she once again squandered a couple of chances. Still, in the fourth game, she managed to take the lead with a break that put her up 3-1 and put her on the path to winning the set.

However, the Ukrainian couldn't hold her serve in the next game, and Muchova managed to even the match again. Both players had chances to get a break in the following games, but neither could convert. Everything went to a tiebreak, where Kostyuk showed more poise than her opponent and was more aggressive, hitting several winners and comfortably winning the tiebreak 7-6 [7-0].

Up until this point, the differences between the two players had been minimal. Both knew they had a good chance of reaching a major quarterfinal again. They both maintained their effectiveness on serve, providing a great spectacle for the crowd at Louis Armstrong Arena. Muchova took advantage of a single break chance in the fourth game and took the lead. A few minutes later, the Czech was serving at 4-2 and faced three break points, but once again showed that she was mentally tougher in the big moments.

Kostyuk had chances to get back in the match but couldn't convert them. Finally, Muchova became strong on her serve and closed out the victory 6-3, 6-7(0), 6-3 after almost 3 hours. The Czech has won all four of her matches at this tournament that have gone to a third set.

In the quarterfinals, her opponent will be none other than the 4-time Grand Slam champion Naomi Osaka—another player who has found inspiration at Flushing Meadows. The Japanese player is back in a Grand Slam quarterfinal for the first time since the 2021 Australian Open after her best win of the season (and best in the last six years), defeating world No. 3 Coco Gauff 6-3, 6-2.

The Japanese star also reached the final of the Canadian Open a few weeks ago, and despite the loss to Victoria Mboko, she has shown once again why she is one of the best players in the world on hard courts. Osaka has 10 wins in her last 11 appearances on hard courts. It is also worth noting that this is the 5th time Osaka has reached a major quarterfinal, and on all four previous occasions, she has gone on to win the title.

The head-to-head record is currently 2-2, including a second-round victory for Muchova at the 2024 US Open, while earlier this season in the Australian Open second round, Osaka got her revenge in three sets.