Serena Williams would struggle to be in the world's top 700 if she was on the men's circuit, according to seven-time Grand Slam champion John McEnroe.
And the male player ranked 701 in the world believes he could beat her, too.
Speaking to US radio station NPR, McEnroe said of world number one Williams, who has won an Open-era record 23 Grand Slams: "If she played the men's circuit she'd be like 700 in the world."
He qualified the comments by saying: "That doesn't mean I don't think Serena is an incredible player, and I suppose anything's possible; maybe at some point a women's tennis player can be better than anybody.