Williams and Sharapova face off in Paris
The 28th seed against a player ranked 451 in the world would not usually command a place on the prestigious Philippe-Chatrier Court at Roland Garros.
But today the French Open will stage a grudge match the like of which grand slam tennis has not seen in a very long time.
Maria Sharapova faces Serena Williams for the first time since the 2016 Australian Open, which was the Russian's last game before a 15-month doping ban.
Williams' dramatic drop down the rankings is due to her maternity leave; she is playing in her first major tournament since having a baby girl in September.
"We are both on a comeback, for two totally different reasons," Williams said, diplomatically, after beating Julia Goerges on Saturday evening. "She's been on her journey for over a year and I just started mine a couple months ago.
"So, you know, it's just something new and different. I don't know what else to say." Except she did know what to say. Williams branded Sharapova's autobiography, in which the Russian described how she heard the American sobbing loudly in the locker room after beating her in the 2004 Wimbledon final, as "100 per cent hearsay".
She went on: "You know, I have cried in the locker room many times after a loss, and that's what I have seen a lot of people do. I think it's normal."
Sharapova claimed that defeat was the reason behind the American's dominant record over her since - overall Sharapova has beaten her fierce rival just twice in 21 matches and not for 14 years.
Unseeded Williams - winner of 23 grand slam singles titles - described Sharapova as the favourite for this one, probably not entirely seriously.
Meanwhile Sharapova knows only too well what she is up against. "You know the challenge that is upon you," she said. "You know, despite the record that I have against her, I always look forward to coming out on the court and competing against the best player."