Two-time US Open champion Naomi Osaka earned her most impressive win since giving birth by knocking out American third seed Coco Gauff to reach the quarter-finals in New York.

Japan's Osaka, who had a daughter Shai in 2023, cruised to a 6-3 6-2 victory in an hour and four minutes.

Gauff, 21, came into her home Grand Slam clouded by uncertainty in her game, and it showed in a subdued performance.

Former world number one Osaka played patiently to draw mistakes out of her opponent, whose forehand was particularly unable to cope with the scrutiny.

Osaka, seeded 23rd, broke into a coy-but-satisfied smile before clapping Gauff, who made a hasty exit, off the court.

Four-time Grand Slam champion Osaka's victory moved her into the last eight of a major for the first time since she won the 2021 Australian Open.

It was also her biggest win by ranking since beating then-world number one Ashleigh Barty at the China Open in 2019.

"I'm a little sensitive, I don't want to cry - I had so much fun out here," Osaka said.

"I was in the stands two months after giving birth to my daughter, watching Coco, and I really wanted an opportunity to come out and play.

"It's my favourite court in the world and it means so much to be back out here."

Osaka will face Karolina Muchova in the last eight after the Czech 11th seed beat Ukraine's Marta Kostyuk.

How Osaka preyed on Gauff's troubles

Two of the sport's most high-profile stars meeting again in New York felt like the first real 'popcorn' match of the tournament, while providing an opportunity for Osaka to show she had regained the level which made her one of the most talented players of her generation.

Ultimately, it ended up lacking entertainment as the 27-year-old Japanese player earned a one-sided win, but emphasised the strides she has made over recent months.

A more measured approach to her powerful baseline game reaped rewards against 2023 champion Gauff.

Osaka smartly asked questions of the clearly-uncertain American, whose forehand breaking down in the rallies was the telling factor in a match lasting little over an hour.

Days before her home Grand Slam, Gauff made a bold move to reshuffle her team in a bid to stem the flow of double faults.

Grip specialist Matt Daly paid the price as in came biomechanics expert Gavin MacMillan, who helped rival Aryna Sabalenka overcome her serving yips.

The drastic measure brought increased scrutiny at what is already a high-pressure tournament - and the added toll clearly affected Gauff.

Looking flustered and frustrated throughout the tournament, her unease was evident from the start against Osaka.

This manifested through her forehand - another area where she has struggled to find consistency over the years.

Eleven unforced errors from this side took the first set away from her. Framing a return from that wing also proved pivotal in the second set.

The mishit brought up two more break opportunities for Osaka at 3-2, with Gauff's more-reliable backhand letting her down on the first point indicated the pressure she was feeling.

For much of the match, it felt like a virtually-capacity 25,000 crowd were slightly conflicted in their support of two hugely popular players.

Gauff led the home challenge in terms of seeding and superstar status, but Osaka - despite representing Japan - grew up in the Queens borough of New York City, where the tournament is held.

Both women have also endeared themselves to fans by eloquently using their voices to shine light on social issues, including racism.

Sensing the younger player needed them more, the crowd tried to rally Gauff as she stared at defeat, but she was unable to recover from losing serve and exited at the fourth-round stage for the second straight year.

Swiatek books extra practice after powering through

Elsewhere on Monday, Wimbledon champion Iga Swiatek extended her winning run at Grand Slams to 11 matches with a 6-3 6-1 demolition of Russian 13th seed Ekaterina Alexandrova.

The Polish second seed wrapped up victory in just 64 minutes in a one-sided affair.

Such was the speed and ease of the victory that Swiatek immediately picked up her phone to text her coach and arrange a practice session.

"I asked him to book 10 minutes of a practice court if it's possible," she said in her on-court interview.

Targeting a second US Open title and second Grand Slam of the season, Swiatek has now reached the last eight or better at all four majors in the same season for the first time.

The six-time major winner could meet American Amanda Anisimova in the quarter-final, in what would be a repeat of July's Wimbledon final when Swiatek thrashed the eighth seed 6-0 6-0.

Anisimova faces Brazilian 18th seed Beatriz Haddad Maia in Monday's evening session.