NEW YORK — Coco Gauff tried to put on a brave face Monday after losing in the fourth round of the US Open for the second year in a row, this time to Naomi Osaka, saying: “I am not going to let this crush me.”

The No. 3-seeded Gauff, who won the first of her two Grand Slam titles at Flushing Meadows in 2023, was undone by a slew of groundstroke errors and failed to do her usual strong job of returning, which all contributed to a 6-3, 6-2 victory for Osaka in just 64 minutes at Arthur Ashe Stadium.

“I just made way too many mistakes — way too many errors — which I feel like that’s the part of my game that I felt the most confident in, coming into the tournament. So, it was kind of a weird match, feeling confident in different areas swapping,” Gauff said. “I mean, it’s disappointing. For sure, it was not the level that I wanted to bring.”

The result was surprising, not just because Gauff was the higher seed — Osaka is No. 23 — and the more recent champion in New York, but also for just how lopsided it was and the way it came about.

Gauff’s serving has been her biggest problem lately, and the shot she recently hired a new coach to help her with during this tournament, but it was good enough Monday afternoon. The other parts of her game were the issue.

She never earned a break chance while returning and finished the match with 33 unforced errors, 20 on her forehand side. Osaka made a total of just 12 unforced errors.

“For me, I felt so discombobulated on the court, because it’s like: I’m serving well, but not returning well,” said Gauff, a 21-year-old from Florida. “The last two years, everybody can agree that’s a weird thought.”

A year ago, her title defense at the US Open also ended in the fourth round. But that one, against Emma Navarro, included 19 double faults. Soon after that tournament, Gauff split from coach Brad Gilbert.

This time, she added biomechanics expert Gavin MacMillan, who helped reconstruct No. 1 Aryna Sabalenka’s serve, the week before play began at Flushing Meadows. There were some difficult moments as she tried on-the-job changes — including in-match tears during the second round — but Gauff is counting on the improvements to pay dividends down the line.

“My goal going into the tournament this year,” Gauff said, “was not to lose the same way that I lost last year.”

She had five double faults against Osaka, along with three aces, while getting broken four times.

“She’s one of the best players in the world. For me, honestly, I have the most fun when I play against the best players. I love when they hit amazing shots or they hit aces, because you know, that’s how they won the tournaments that they won,” Osaka said about Gauff. “I always see it as a challenge. I like challenges.”

It has been an up-and-down Grand Slam season for Gauff, who lost in the quarterfinals at the Australian Open in January, won the French Open in June and exited in the first round at Wimbledon in July.

“It’s been a tough post-French Open for me, for sure. I know the improvements that I need to make, and I feel like I’m making the right decision by making them,” Gauff said.

“I feel like I put so much pressure on myself at my age, at 21, and I realize how much the girls on tour are being successful at 25, 26, at those ages. For me it just gets me excited to realize if I have four more years of just working as hard as I am right now, and actually doing the right things, where my game could be,” she said. “It has obviously improved in the last four years. … So, I think if I can make that same jump of improvement, it’s a lot to be excited [about] for the future.”