John McEnroe's belief that Serena Williams would be ranked as low as 700 in the world if she played on the men's tour has drawn short shrift from the 23-time women's singles grand slam champion.
Williams' major haul is a record for any tennis player - male or female - in the Open era, but McEnroe courted controversy by suggesting the 35-year-old would struggle on the ATP World Tour.
Williams, who is set to be out of action until next year after announcing in April she is expecting her first child, responded on Twitter: "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 is currently placed fourth in the WTA rankings despite her absence from the circuit since January - when she captured a seventh Australian Open crown - and she briefly returned to the top of the standings shortly after announcing her pregnancy.
McEnroe, a former world number one who won Wimbledon three times and the US Open on four occasions, had earlier said of his fellow American in an interview with US radio station NPR: "If she played the men's circuit she'd be, like, 700 in the world.
"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.
"I just haven't seen that in any other sport, and I haven't seen it in tennis. If she had to just play the men's circuit, it would be an entirely different story."
McEnroe had earlier referred to Williams as the "best female player ever - no question".
His ranking comments came after he was asked by the interviewer to whether there was need to qualify the statement with the word female.
