Naomi Osaka and coach Patrick Mouratoglou are done working together after less than a year, the four-time Grand Slam champion announced Sunday on social media. “Merci Patrick,” Osaka began her post, with a photo of her hitting a practice serve while he stands nearby.

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

Naomi Osaka is making a major change at the start of the North American hard-court swing as the former world No. 1 decided to call time on her partnership with coach Patrick Mouratoglou.