Serena Williams fired back via Twitter on Monday after John McEnroe said that if she played on the men's circuit, she'd be "like No. 700 in the world."
In an interview Sunday, McEnroe said that Williams has earned the designation as the greatest woman to play tennis, but he wouldn't put her in the category of greatest to ever play tennis.
"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," McEnroe said.