Four-time Grand Slam singles champion Naomi Osaka will work with Polish coach Tomasz Wiktorowski on a trial basis, following her split from Patrick Mouratoglou after less than a year together.

Osaka announced the parting with Mouratoglou, former coach of Serena Williams, on social media Monday. She then went on to defeat Canadian qualifier Ariana Arseneault 6-4, 6-2 in her first-round match at the WTA Canadian Open in Montreal.

Wiktorowski has a strong coaching pedigree, having guided Poland's Agnieszka Radwańska to a Wimbledon final and world No. 2 ranking (2011-2018), and Iga Swiatek to four Grand Slam titles and the world No. 1 ranking (late 2021-October 2024).

Osaka, currently ranked 49th, had been working with Mouratoglou since last September. Under his guidance, she reached the Auckland final in January but retired due to an abdominal injury. She also won a WTA 125 title in May, her first since the 2021 Australian Open. Osaka will next face 13th seed Liudmila Samsonova in the second round.