Japan's Naomi Osaka, a four-time Grand Slam singles champion, will work with Polish coach Tomasz Wiktorowski on a trial basis after splitting with Patrick Mouratoglou after less than a year together.

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.