Serena Williams has spent years dealing with pointless misogyny from those in and out of the tennis world.

But retired great John McEnroe took the one-sided feud up a level recently, with the release and promotion of his new memoir, "But Seriously."

While being interviewed on NPR, McEnroe declared that if if the tennis star "played the men's circuit, she'd be like 700 in the world," before adding "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. [...] But if she had to just play the circuit – the men's circuit – that would be an entirely different story."

While McEnroe and others have lavished praise on Williams as one of the greatest, if not the greatest, female tennis player of all time, it's always qualified with "female."

Williams in particular has always seemed to draw questions about how she'd do against male players, including McEnroe himself, who told Jimmy Kimmel in 2015 that he'd beat Williams even at age 56.

Williams seemed to have little time for McEnroe, tweeting shortly after his interview that she was getting ready to have a baby and wanted no part of his hypothetical tennis ranking.

The debate over whether women could beat men is a common trope in sports coverage, almost always being used to downplay or qualify the accomplishments of female players.

For example, in 2010, ESPN devoted an entire column to whether the record-setting University of Connecticut (UConn) women's basketball team, which had just broken University of California, Los Angeles' streak of 88-straight wins, could beat the worst men's team in Division I basketball. Essentially, UConn's achievement was important, but not as important as whether they'd beat a bad men's team.

Tennis, in particular, has seemed obsessed with pitting men against women, going as far back as an 1888 match between the men's and women's Wimbledon champions. In the most famous example, the "Battle of the Sexes," retired men's player Bobby Riggs lost to current player Billie Jean King, prompting rumors that he threw the match for money.

Recent research has revealed that despite the physiological differences between men and women, there's little difference in the difficulty or level of skill required to succeed in women's tennis, but the debate over which gender is "better" rages on.

Williams has mostly taken the debate in stride, playing along, but being careful never to embarrass herself. In 2013, she said a proposed match between her and champion Andy Murray would be "fun" but that she would lose quickly and decisively. "Men are a lot faster and they serve harder," she told David Letterman at the time. "They hit harder. It’s just a different game."

At the same time, she's made it clear that she believes the debate over her place in the tennis pantheon only exists because of her gender, as she told rapper Common during an ESPN interview in December, "if I were a man, I would have 100 percent been considered the greatest ever a long time ago."

For his part, McEnroe was offered a chance to apologize for the comment during an interview on Tuesday, and refused.