Japan's Naomi Osaka withdrew from her WTA Western & Southern Open semi-final match on Thursday in New York to protest the police shooting of an unarmed black man in Wisconsin. Osaka, a two-time Grand Slam champion, was to have faced Belgian Elise Mertens.

More important than tennis

"Before I am an athlete, I am a black woman. And as a black woman, I feel as though there are much more important matters at hand that need immediate attention, rather than watching me play tennis," Osaka posted in a statement on Twitter. "I don't expect anything drastic to happen with me not playing, but if I can get a conversation started in a majority white sport I consider that a step in the right direction."