NEW YORK — Former champions Coco Gauff and Naomi Osaka will go head-to-head in a blockbuster fourth-round matchup at the US Open on Monday night, after booking their places in the last 16 in contrasting styles.

Gauff cruised past Magdalena Frech of Poland 6-3, 6-1, while Osaka battled past Australia’s Daria Kasatkina 6-0, 4-6, 6-3 to make the fourth round of a major for the first time since she won the Australian Open in 2021.

This will be their sixth match in all, and first at the US Open since 2019 — their first meeting — when Osaka beat the then-15-year-old Gauff 6-3, 6-0. Gauff got her revenge at the Australian Open in 2020 in their next match, then they traded off the next two. Most recently, Gauff advanced in Beijing in 2024, when Osaka retired through injury at one set all, making the overall record 3-2.

It’s a pivotal match for both players. For Gauff, it’s the chance to reach the quarters for the third time in four years. For Osaka, it’s an opportunity to reestablish herself at the business end of a major for the first time since she became a mother.

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What Gauff has to do to win

One part is simple: If she serves well, she will have a great chance to win.

No one has served more double faults than her in the past three years — she is closing in on 1,000 since the start of 2023. And her serve remains a work in progress under the guidance of Gavin MacMillan, the man who cured Aryna Sabalenka’s serving woes a few years ago.

Gauff has been cutting down on her pace in an effort to get more first serves in and take the pressure off her second serve, which is still shaky at times. Osaka is an aggressive returner, so anything short will be punished, which in itself will be a pressure. But no one battles harder than Gauff, and she will fight like her life depends on it.

But even when she doesn’t serve well, Gauff has shown remarkable resilience, and as she proved at the French Open, she can even win slams when not at her best.

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Naomi Osaka prevails in 3 sets at US Open

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What Osaka has to do to win

Osaka has been returning even better than Gauff so far in this tournament, making 83% of balls back, on average, and winning an average of 38% when returning first serve and a massive 73% when returning the second serve.

That spells trouble for Gauff if she misses first serves too often, because Osaka will pounce on anything short. Her movement is vastly improved over recent months and her confidence is up. When she is in position to crack a forehand or backhand, she’s mighty dangerous, dominating the 0-4 shots category.

When Osaka is at her best, she excels in first-strike tennis, and if she continues to hit the ball the way she has been, she should get plenty of opportunities to dominate rallies against Gauff, whose counterpunching skills will be tested.

What they’re saying about each other

Gauff on their 2019 US Open match: “I remember it was a tough moment for me because it was a hyped-up match. I guess I put way too much pressure on myself thinking I maybe had a chance in that moment to actually do something, which I definitely did, but I think it was just I felt more expectation that I should than maybe belief. Then when I played her in Australia, that was more belief than expectation. It would be a cool kind of déjà vu type of situation, but hopefully it will be a different result.”

Osaka on Gauff: “Can somebody come to the match and cheer for me because it’s kind of tough playing an American here? I kind of see her as a little sister so it’s kind of cool to be playing her here again. To be playing her again after six years, I don’t know if that makes me old, but just to be at this point of my life and to be playing her again is honestly, for me, feels kind of special. I’m honestly excited to play her now, because I feel healthy, and I just want to see what happens.”

Who will win?

Considering that Osaka has not reached the quarters of a Slam since 2021, it’s strange that this match feels like a bit of a toss-up. But she has confidence from reaching the final in Canada and is beginning to look like the woman who has four Grand Slams to her name, while Gauff is still fighting herself as she tries to fix her service action.

With the exception of their last meeting, when Osaka retired injured after the second set, the player who wins the first set has won in all the other four clashes, so a fast start is imperative. Gauff will have the crowd on her side but that brings its own pressure, while Osaka is playing great tennis again, so this threatens to be the kind of match that could spark a real rivalry for the next few years.

Prediction: Three sets, to Osaka.