IIRC Serena was asked by Letterman if she would win against the men in tennis. She quickly answered no. The men’s game is much faster and stronger.
I always have believed that the reason Bobby Riggs (55) lost to Billie Jean King (30) was simple. He bet on her (and made a fortune!).
https://en.wikipedia.org/wiki/Bobby_Riggs#%22Mother's_Day_Massacre%22_and_%22Battle_of_the_Sexes%22