NEW YORK — Naomi Osaka eliminated Coco Gauff 6-3, 6-2 in 64 minutes at the US Open on Monday to reach her first Grand Slam quarterfinal in more than 4½ years.

Osaka advances to her fifth major quarterfinal, and first since giving birth to daughter Shai in July 2023. Every time Osaka has made the quarterfinal round of a major, she has gone on to win it, her last Slam coming at the 2021 Australian Open.

The No. 23 seed Osaka was better throughout than No. 3 Gauff, whose repeated mistakes made the difference in Arthur Ashe Stadium.

“I was super locked in, to be honest,” said Osaka, a 27-year-old who was born in Japan and moved to the U.S. with her family at age 3. “I was really locked in. I felt like everyone wanted to watch a really great match, and I hope that’s what you got.”

Osaka displayed the demeanor, big serve and booming strokes that have carried her to four major championships, all on hard courts. Those titles came at the US Open in 2018 and 2020, and at the Australian Open in 2019 and 2021.

It was at the French Open later in 2021 that Osaka helped spark a global conversation about mental health by revealing she felt anxiety and depression. She then took a series of breaks from the tour.

That most recent trophy at Melbourne Park was the last time Osaka had even made it as far as the fourth round at any Slam event until this match against Gauff, a 21-year-old from Florida who owns two major trophies. The first came at Flushing Meadows in 2023 and the second at the French Open this June.

For Osaka, this marks a return to her best play since she rejoined the tour after a 17-month maternity leave.

“I’m a little sensitive and I don’t want to cry, but honestly, I just had so much fun out here,” said Osaka, who first played Gauff back at the 2019 US Open, also at Ashe, and won that one, too.

“I was in the stands like two months after I gave birth to my daughter, watching Coco. I just really wanted an opportunity to come out here and play,” Osaka told the crowd. “This is my favorite court in the world, and it means so much for me to be back here.”

Gauff came out jittery at the start. Her problematic serve was fine; other strokes were the problem. She finished with 33 unforced errors — far more than Osaka’s 12.

Plus, Osaka’s serving and returning were terrific. She won 32 of the 38 points she served — 15 of 16 when first serves landed in — and never faced a break point. She also converted all four break chances she earned.

Trying to rework her serve during this tournament with the help of biomechanics expert Gavin MacMillan, Gauff got broken right off the bat and was down 2-0 after just five minutes, dropping eight of the initial nine points while making five unforced errors.

Whether it’s what the prematch strategy dictated or because of how the beginning unfolded, Gauff cranked up the velocity in her second service game. The results were unimpeachable. She hit four first serves in — each arriving no slower than 110 mph, with a high of 115 mph — and held at love with a pair of aces and a pair of service winners.

Still, the key difference was that Osaka used her big forehand, her best stroke, to go after Gauff’s forehand, her worst stroke, and it worked wonders.

By the end of the first set, Gauff had made 16 unforced errors and Osaka only five. By the end of the match, 20 of Gauff’s unforced errors were off the forehand side.

On Wednesday, Osaka will face No. 11 seed Karolina Muchova — who got past 45-year-old Venus Williams in three sets in the first round of this US Open — for a berth in the semifinals. Muchova, the 2023 French Open runner-up and a semifinalist in New York the past two years, advanced to the quarterfinals with a 6-3, 6-7 (0), 6-3 victory No. 27 Marta Kostyuk of Ukraine.

Muchova, 29, from Czechia, became the fourth woman in the Open era to win a three-setter in four straight rounds at Flushing Meadows, joining Lesley Hunt (1978), Sylvia Hanika (1979) and Jelena Ostapenko (2023).

ESPN Research and The Associated Press contributed to this report.