Naomi Osaka breathed a sigh of relief after outlasting Elise Mertens in a US Open thriller to stay in her "favourite tournament" and tee up a fourth-round clash with Elena Rybakina.

She had to dig deep to earn her 6-3 3-6 7-5 victory in two hours and 39 minutes on Louis Armstrong Stadium.l

Osaka – a two-time Flushing Meadows champion in 2018 and 2020 – looked to be in trouble when Mertens went a break up in the deciding set, after the players split the first two.

Osaka then called a medical timeout and received treatment on her leg, having thrown her racket to the ground and berated herself earlier in the contest.

And that break helped steady Osaka's nerves as she got the contest back on serve, though she squandered her first match point against Mertens' serve at 5-4 up.

Two more missed match points came and went for the four-time grand slam champion in Mertens' next service game, but Osaka made her fourth count as Mertens' forehand landed wide to the right.

Reflecting on what had been an emotionally charged contest, Osaka said: "I have no problem losing a match if I feel like I'm playing good, but I just felt like I was playing terribly.

"This is my favourite tournament, and I don't know, there were just a bunch of negative emotions – I felt like I didn't want to go out that way.

"I just want to have a fun match. I think this match was a lot emotionally, and I just want to have a fun time."

Never backs down @naomiosaka secures her spot in the Round of 16.#USOpen pic.twitter.com/2MMsnbbfuP

— wta (@WTA) September 6, 2026

Things will not get any easier next time out for Osaka, as she faces world number two Rybakina for a place in the quarter-finals.

Rybakina downed Ukraine's Yuliia Starodubtseva 7-6 (8-6) 6-3, and she is now just two wins away from overhauling Aryna Sabalenka at the top of the WTA rankings, as a semi-final berth will secure that honour even if the Belarusian wins a third straight US Open crown.

Also on Saturday, Iva Jovic outlasted Alexandra Eala 7-5 3-6 7-5 in just over three hours, reaching the fourth round of her home slam for the very first time.

That match was a chaotic one, with Jovic managing nine breaks to Eala's eight in front of a vocal crowd at Arthur Ashe Stadium, and the 18-year-old's reward will be an all-American matchup against 2023 champion Coco Gauff.

Osaka replicates Date and Sugiyama

Osaka is only the third Asian woman in the Open Era to reach the round of 16 at a grand slam on all three surfaces in the same season, after her fellow Japanese players Kimiko Date (in 1995) and Ai Sugiyama (in 2003).

Her performance on Saturday was far from perfect, as she mixed 39 winners with 41 unforced errors, but she managed to save eight of the 11 break points she faced, while converting one more than Mertens (four of 16).

Osaka will now look to reach her seventh grand slam quarter-final and her second this year, after going out at that stage at Wimbledon.

To do so, she will have to become the first player to defeat both Rybakina and Sabalenka at WTA or grand slam level this season. Their only previous meeting at Tour level went the way of the Kazakhstani player, in the Toronto quarter-finals this year.