Naomi Osaka reached the fourth round of the 2026 US Open after surviving a tense three-set contest and a lower-leg problem against Elise Mertens in New York.
The No. 13 seed won 6-3, 3-6, 7-5 inside Louis Armstrong Stadium, closing the match on her fourth match point after two hours and 38 minutes. Osaka required treatment late in the deciding set, but recovered sufficiently to produce her strongest sequence when the match was most uncertain.
Osaka vs Mertens: match result
- Winner: Naomi Osaka
- Score: 6-3, 3-6, 7-5
- Round: Third round
- Venue: Louis Armstrong Stadium, New York
- Match time: Two hours, 38 minutes
- Next stage: Fourth round
Osaka began with control. She held her opening service games, took advantage of two Mertens double faults to secure the first break and saved both break points she faced while serving for the opening set. She needed four set points, but completed the first stage of the match 6-3.
Mertens changed the rhythm in the second set. After falling behind an early break, the Belgian steadied her game while Osaka's unforced-error count rose. The No. 24 seed levelled the contest 6-3 and forced a deciding set between two players who know each other's patterns unusually well.
The injury scare in the third set
The match shifted again when Osaka showed discomfort in her lower leg during the final set. She called for the trainer after holding serve for 3-4, creating immediate doubt over whether she could finish at full intensity.
Instead of allowing the physical issue to decide the contest, Osaka shortened the problem in front of her. She won three consecutive games to move 5-4 ahead and kept taking the initiative when points became tense. Mertens resisted, but Osaka eventually broke through at 6-5 and converted her fourth match point.
The sequence was significant because it required more than shot-making. Osaka had to manage movement, emotion and risk at the same time. Long rallies could test the leg, while forcing the pace too early could increase errors. Her ability to find the necessary balance carried her into the second week.
Why this US Open run matters
Osaka is a two-time US Open champion, winning in 2018 and 2020, and New York remains the Grand Slam where her best results have most often appeared. This is the fifth time in 10 main-draw appearances that she has reached the tournament's second week.
There is another measure of progress. For the first time in her career, Osaka has reached at least the fourth round at three Grand Slams in the same calendar year. She also made the fourth round at Roland Garros and the Wimbledon quarterfinals in 2026.
That consistency matters for a player whose reputation was built on winning the biggest hard-court titles. A deep run at one major can be a surge of form; repeated second-week appearances suggest a more stable competitive level across surfaces.
A familiar opponent and a difficult test
The meeting was the 10th tour-level match between Osaka and Mertens. Osaka has faced no opponent more often in her professional career, so neither player entered without a detailed understanding of the other's strengths.
Mertens' ability to absorb pace, redirect the ball and extend exchanges made her especially dangerous once Osaka lost accuracy in the second set. Familiarity can reduce easy tactical surprises, leaving execution and physical resilience to decide the important points.
Osaka's final-set response therefore offered an encouraging sign. She did not dominate every phase, but she solved a match that changed shape repeatedly.
What comes next for Osaka?
The immediate question is physical recovery. A lower-leg problem can be difficult to evaluate from the outside, and the demands increase as a Grand Slam enters its second week. Osaka and her team will have to assess how the leg responds after treatment, rest and the accumulated load of a long match.
Her tennis, however, has already carried her through three rounds. She remains one of the most powerful first-strike players in the women's draw, and her history in New York gives every opponent a reason to take her seriously.
The women's tournament is also developing quickly around her. Coco Gauff reached the fourth round with a straight-sets victory over Cristina Bucsa; read our report on Gauff's US Open progress. For dates, sessions and viewing information, see the US Open 2026 schedule guide.
Osaka's victory was not a clean procession. It was a test of adjustment under pressure, completed while her movement was under scrutiny. At a tournament where she has twice lifted the trophy, reaching the fourth round in those circumstances may prove more valuable than an easy win.
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