Serena Williams has fired back at John McEnroe after he claimed that she would be number 700 in the world if she played on the men's circuit.
The world number four, who is currently taking a break from tennis to prepare for the birth of her first child, is one of the most dominant sporting figures in the game.
The 35-year-old American has won 23 Grand Slam titles, while Roger Federer, who is the most successful player currently competing on the men's circuit, has 18.
During an interview with NPR, McEnroe praised Williams's ability, but questioned whether she would be as dominant if she played against her male counterparts.
"That doesn't mean I don't think Serena is an incredible player. I do, but the reality of what would happen on a given day is Serena could beat some players, I believe, because she is so incredibly strong mentally," said McEnroe. "But if she had to just play the circuit - the men's circuit - that would be an entirely different story."
In response to his comments, Williams tweeted: "Dear John, I adore and respect you but please please keep me out of your statements that are not factually based. I've never played anyone ranked "there" nor do I have time. Respect me and my privacy as I'm trying to have a baby. Good day sir."
Williams was pregnant when she won the Australian Open in January.