Osaka's time with Mouratologou followed an up-and-down sequence of promising signs and frustrations with either injury or close-run defeats.

The news comes after Naomi Osaka lost her second match at the D.C. Open and just before she begins competing in Toronto.

Osaka, a four-time Grand Slam champion, has been in a career rut for years. Mouratoglou joined her staff in September of 2024 and there hasn't been much improvement. Osaka has not made it past the third round of a Grand Slam tournament since 2021 when she won the Australian Open. Now she will look for a new coach to help bring her back to form.