Former World No.1 Naomi Osaka has announced the end of her four-year working relationship with coach Wim Fissette.

"[Four] years, [two] Slams and a whole lot of memories," Osaka wrote in a post to her Instagram stories confirming the split on Friday. "Thanks Wim for being a great coach and an even greater person. Wishing you all the best."

Fissette and Osaka worked together in two chapters -- first from the 2019 offseason to the summer of 2022, before they reunited last summer when Osaka began training ahead of her return to tennis following the July 2023 birth of her daughter, Shai. Osaka won the 2020 US Open and 2021 Australian Open titles under his guidance, and also reached the finals of the 2020 Cincinnati Open and the 2022 Miami Open.

The announcement comes eight months into Osaka's return to the Hologic WTA Tour, which began at the Brisbane International in January. Despite a refreshed, optimistic outlook on her career, wins over six Top 20 players in her comeback, and a current ranking of No. 75, Osaka has only reached two quarterfinals in the 16 tournaments she has played so far this season.

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The former World No.1 last played at the US Open, where she was beaten in the second round by eventual semifinalist Karolina Muchova; she did not pass the second round in any of the four Grand Slam tournaments in 2024, though she did earn her first Top 10 victory since 2020 against Jelena Ostapenko in the first round in Queens. 

"It's been a little difficult because obviously I can only gauge how I'm doing by results," Osaka confessed after losing to Muchova 6-3, 7-6(5). "I feel faster. I feel better, but I lost in the second round. So it's a little rough.

"But, also, it's been fun playing a lot of tournaments. It's been a commitment for sure, but I've been able to go to different cities that I've never been to. ... It's a little rough because I do take these losses really personally. It's like a dramatic word, but I feel like my heart dies every time I lose. It sucks a lot, but I've been trying to be more mature and learn and talk more about them."

"I feel like I'm working way harder than I've ever worked in my life, so it needs to turn into something," she added. "Well, it doesn't need to, but I think it will."