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’s tennis career has been, quite frankly, a rollercoaster. Not just any rollercoaster, but one of those heart-in-your-throat drops-with-a-couple-of-loops type of rides.

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.