NEW YORK -- Born four months apart, both scuffling in recent weeks, Jelena Ostapenko and Naomi Osaka entered this US Open hoping to recapture the rare feeling that comes with being a Grand Slam champion.

They met on Tuesday in the first round, the first time in five years that two major winners faced each other here at this early stage. As you might have expected, there were fireworks out in Louis Armstrong Stadium. In the end, it was an extremely absorbed and engaged Osaka, prevailing 6-3, 6-2.

It was her first Top 10 win in four-and-a-half years.

US Open: Scores | Draw | Order of play

Osaka was credited with 19 winners, against only five unforced errors. She won 39 of her 50 service points and was not broken.

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Osaka has now won 23 of her 28 matches (.821) at the US Open -- among current players with 10-plus main-draw matches played here, only Bianca Andreescu (.857) has a higher winning percentage.

Technically, this was an upset, but Osaka did not look like a player who stands No.88 in the PIF WTA Rankings and needed a wild card to get into the main draw. Next for her on Thursday is another popcorn match against another unseeded dynamo, Karolina Muchova, a straight-sets winner over Katie Volynets.

The return of Osaka has been one of the more intriguing storylines of 2024. The four-time Grand Slam champion -- she won the US Open in 2018 and 2020 -- stepped away from the game two years ago. After giving birth to daughter Shai, she arrived in Brisbane this year profoundly changed by the experience.

She’s played a more adventurous schedule and has been extremely outgoing in her interactions with the media. Even back in January, the 26-year-old who represents Japan talked about pointing toward the US Open as a realistic target to assess her progress. The results, understandably, have been mixed.

One month later, she reached the quarterfinals at the WTA 1000 in Doha and the third round at both Indian Wells and Miami. On clay, Osaka played her way into the round of 16 in Rome but her signature match of the year came in Paris -- and it was a loss. Facing Iga Swiatek on her favorite court, Philippe Chatrier at Roland Garros, Osaka extended the World No.1 to three sets before falling 7-6 (1), 1-6, 7-5. It was the only set Swiatek dropped on her way to a fourth title in five years.

Osaka, attacking her weakness on her worst surface, played three grass events, going 3-3. She lost in the first round of the Olympics, split matches in Toronto, failed to qualify in Cincinnati and came to New York, after a two-year hiatus, with an 18-15 record. Having spent some of her formative years in Long Island, attending the US Open as a child, this has always been a special tournament for her.

“I made a promise to myself to be as confident as I can in the fact that I am who I am,” Osaka told reporters before the tournament. “I feel like, for me, throughout the year I have had really hard matches, and it kind of dipped my confidence a little. I wouldn’t say that I played bad tennis. I just would say that I played really good players, and I also learned a lot.

“I do think coming to this specific tournament helps me out. But also, whenever I step foot here, I don’t really think about the two tournaments I won. I just think about how I felt when I was a kid. It's more of a childhood nostalgia that I really enjoy.”

It’s been more than seven years since Ostapenko won the 2017 French Open and six years since she reached a career-high No.5 among WTA Tour players.

But the 27-year-old from Latvia has reinvented herself in 2024, entering play here ranked No.10. She began the year by winning 13 of 15 matches, including titles in Adelaide and Linz. Ostapenko was a quarterfinalist in Rome and Wimbledon, losing respectively to Aryna Sabalenka and eventual champion Barbora Krejcikova.

The first real drama in the match came in warmups, when Osaka unveiled her newest kit, a lime-green ensemble that features four tiers of ruffles and a white bow in the back.

And then, despite the breezy conditions, the two produced some excellent ball-striking. It wasn’t until 25 minutes in that Osaka forged the first break point of the match -- an errant backhand gave her a commanding 5-3 lead. That produced her third consecutive “Come on!” with each one successively louder.

Riding that considerable wave, Osaka broke Ostapenko to open the second set. She repeated that feat in the seventh game and eventually served out the 64-minute exercise, converting her third match point.

Osaka attended the US Open last year as a spectator and was inspired watching Coco Gauff’s run to the title.

“At that time, I didn’t know at what level could I play,” Osaka said. “Obviously I want to, like, be in the Top 10, and I want to do all these things, but I still, in the back of my mind, remember not being able to run, if that makes sense, or not being able to do a situp. Yeah, in some moments I’m really amazed. But I came here with, like, the specific goal of doing the absolute best that I can.

“I was watching in the stands last year, and I promised myself this is going to be the tournament where I do the best. Or hopefully here or Japan or during the Asian swing. That’s kind of where I put all my energy. I guess we’ll see what happens.”