The two biggest names in women’s sport have been going head-to-head for most of their careers, playing 20 times.
Sharapova was on top at the start, beating Williams in the 2004 Wimbledon final and the decider of the Tour Championships later that year.
But that was as good as it got for the towering Russian, who has since been on the wrong end of the scoreline 17 times straight.
It began with an epic semi-final at the 2005 Australian Open, with the American scraping home in a 2-6, 7-5, 8-6 thriller.
“I just remember hitting an inside-out forehand when I was down match point,” said Williams, who rated the win among the best of her career. “I remember hitting it as hard as I could.
“I remember obviously winning, and that was really great.”
Since then she has been unrelenting, whipping Sharapova in the finals of the Australian Open in 2007 and 2015, and she is gunning to keep the pressure on when they meet in the last eight at Melbourne Park on Tuesday.
“I just feel like I’m really confident in my game right now, not against her or against any other opponent, I’m just really looking at me right now,” she said.
“And I feel like if I can just continue to play well, then it could be good.
“But every match is new. You know, she always brings in something new and something special. She’s very consistent as well.
“She knows how to be — one player that’s always consistently winning and training and working hard and winning matches.”
18th time lucky?
While the six-time Australian Open winner is clearly fancied to make the semi-finals given her record against Sharapova, who won her sole Australian Open title in 2008, she is not getting ahead of herself.
Asked who had more pressure, a player on a long winning streak or the opponent who has been losing, Williams replied: “I think the person who’s winning could definitely feel the pressure because there is a lot of expectations.
“But in this situation, I don’t have anything to lose because I’m just here — every tournament for me is just a bonus at this point in my career. So it’s an interesting place to be at.”
Despite her dismal record, Sharapova remains unfazed, insisting she is always looking to improve and that she uses the losses against the mighty American to examine what she could do better.
“Absolutely. It’s not like I think about what I can do worse!” she said. “You’re always trying to — always trying to improve. I got myself into the quarter-final of a Grand Slam.
“There is no reason I shouldn’t be looking to improve and to getting my game in a better position than any other previous round. It’s only going to be tougher, especially against Serena.”
To finally end her jinx, Sharapova will have to counter the Williams serve, while ensuring her own is firing — as it was against Belinda Bencic in the fourth round, when she sent down a career-high 21 aces.