Japanese women's tennis star Naomi Osaka, an outspoken critic of racial injustice, expressed dismay Tuesday that the conviction of a white police officer in the United States for killing a black man should have been in doubt.

The video footage of Minnesota police officer Derrick Chauvin kneeling on the neck of George Floyd last summer until he died intensified outrage and sparked worldwide demonstrations against police brutality directed toward African Americans.

Naomi Osaka is pictured wearing a "Black Lives Matter" t-shirt ahead of her semifinal match against Elise Mertens at the Western and Southern Open in New York.(Kyodo)

Posting on social media platform Twitter, Osaka called the decision to convict "clear as day," but said she could not celebrate out of sadness for the fact that the verdict was in doubt in a nation where police violence against African Americans routinely goes unchecked.

"The fact that so many injustices occurred to make us hold our breath toward this outcome is really telling," wrote Osaka, who at last year's U.S. Open wore masks bearing Floyd's name and that of others who died at the hands of police.

Osaka, whose mother is Japanese and father Haitian, was born in Japan but grew up in the United States.

The National Basketball Association and its players association released a joint statement that said, "We are pleased to see justice has been served...and will redouble our efforts to advocate for meaningful change in the areas of criminal justice and policing."

Major League Baseball's statement read: "In the wake of today's verdict, Major League Baseball hopes to contribute to the healing process by continuing to work with our players...to advance the values of social justice, equality, diversity and inclusion."

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