Serena Williams has won 23 Grand Slams, more than anyone in Open Era history, and her tennis success has led many sports fans to label her the G.O.A.T: Greatest of All Time.

Yet, fellow tennis legend John McEnroe disagreed with this statement in a radio interview with NPR this weekend, stressing that he doesn’t think Williams deserves the title without including the word “female.”

“If she played the men’s circuit, she’d be like 700 in the world,” McEnroe said.

Here’s the bulk of the transcript:

NPR’s Lulu Garica-Navarro: We’re talking about male players but there is of course wonderful female players. Let’s talk about Serena Williams. You say she is the best female player in the world in the book.

McEnroe: Best female player ever — no question.

Garcia-Navarro: Some wouldn’t qualify it, some would say she’s the best player in the world. Why qualify it?

McEnroe: Oh! Uh, she’s not, you mean, the best player in the world, period?

Garcia-Navarro: Yeah, the best tennis player in the world. You know, why say female player?

McEnroe: Well because if she was in, if she played the men’s circuit she’d be like 700 in the world.

Garcia-Navarro: You think so?

McEnroe: Yeah. That doesn’t mean I don’t think Serena is an incredible player. I do, but the reality of what would happen would be I think something that perhaps it’d be a little higher, perhaps it’d be a little lower. And on a given day, Serena could beat some players. I believe because she’s so incredibly strong mentally that she could overcome some situations where players would choke ’cause she’s been in it so many times, so many situations at Wimbledon, The U.S. Open, etc. But if she had to just play the circuit — the men’s circuit — that would be an entirely different story.

When Williams played in, and dominated, the US Open in 2012, McEnroe said he considered Williams to be “one of the all-time greatest athletes, period. Man or woman,” and he offered almost identical praise in 2015 after Williams’ victory at Wimbledon.

However, he has now clarified that he thinks Williams is should only be considered the greatest “female” athlete, with “female” being the key part.

“Maybe at some point a women’s tennis player can be better than anybody,” McEnroe said. “I just haven’t seen it in any other sport, and I haven’t seen it in tennis. I suppose anything’s possible at some stage.”

The debate over “greatest athlete of all time” or “greatest female athlete of all time” is not new for Williams.

In 2016, just before she won Wimbledon and earned her 22nd Grand Slam title, Williams responded to a reporter who asked her what she thought when people called her one of the greatest female athlete of all time.

She responded simply, attempting the quiet the critics.

“I prefer the word ‘one of the greatest athletes of all time,’ ” Williams said.

Nike, Williams’ sponsor, launched an ad ad reinforcing this idea after Williams’ win.

The ad includes a series of words that describe Williams including “winner,” “pro,” “focused,” “#1” and then “greatest female athlete ever.” As the seconds tick by at the end of the ad, the word “female” disappears, leaving just the line “greatest athlete ever” written across the screen.”

Williams, who is currently pregnant and has opted out of Wimbledon this year, said she plans to return to the court after her pregnancy, and she will now have additional motivation to continue to win.