Four-time Grand Slam champion Naomi Osaka retired from her opening match on Tuesday at the WTA Toronto Masters with lower back pain, raising injury concerns with the US Open looming.

Four-time Grand Slam champion Naomi Osaka made a triumphant return from a two-month layoff by defeating Chinese teen Zheng Qinwen on Tuesday at the WTA San Jose hardcourt tournament.

 Former world number one Naomi Osaka's coach Wim Fissette said on Wednesday that the pair had ended their partnership after working together since 2019.

Naomi Osaka was knocked out of the French Open in the first round on Monday, 12 months after controversially quitting the tournament.