American teenage tennis star Coco Gauff can help "change the world for the better"," says 18-time Grand Slam champion Martina Navratilova.
At a peaceful protest in Florida last month, Gauff urged people to vote and speak out against racism.
"I smile so much when I see the reach she already has now, and she will have in the future," said Navratilova.
She told BBC Radio 4's Today Programme: "She is just so poised on and off the court, she was brought up with great qualities and it shows how she plays and it shows how she's active now politically.