That was at the WTA Championships, when the Russian was just over six months short of her 18th birthday. Nearly nine years later, she will try to stop Williams from winning her 16th grand slam title in the French Open final today, where Sharapova has to beat overwhelming odds to defend her title.
Williams leads 13-2 against Sharapova and has won their past 12 matches on all surfaces.
"Well, I'd be lying if it doesn't bother me," Sharapova said. "I don't think that it would be a pretty competitive statement if I said it didn't. I would love to change that around."
Comparing Thursday's semi-finals, the odds of that happening look extremely thin. Williams crushed last year's finalist Sara Errani 6-0, 6-1, in 46 minutes, spending barely a third of the time on court that Sharapova did in her gritty 6-1, 2-6, 6-4 win against Victoria Azarenka.
"I have never played Maria here," said Williams, who won her only Roland Garros title 11 years ago. "We're both excited to be this far."
Sharapova beat Williams in the 2004 Wimbledon final, but in their past 11 matches has won only two of the 33 sets contested. One of those was in the final at Miami, in March. But to find the other requires going back to 2008, when Sharapova lasted three sets on clay at Charleston.
"Whatever I did in the past hasn't worked, so I'll have to try to do something different and hopefully it will," the 26-year-old Sharapova said. "I don't feel like I have taken my chances and opportunities."
They are the top two women in the rankings and seedings, No 1 Williams and No 2 Sharapova.
Williams' winning streak stands at 30 matches, the longest single-season streak on tour since 2000. "She's playing some of the best tennis of her career," Sharapova said.
The 31-year-old Williams has other factors working in her favour. She has been doing everything to get the fans on her side for the final. After her victory, the American once again answered questions in French, and even said "J'aime le public" - "I love the crowd."
She also reminded them how long it has been since she won at Roland Garros. In somewhat muddled French, but with a good accent, she said: "Je reste encore apres 11 ans, c'est tres magnifique pour moi."
But the point was made, because it roughly translated as "I'm still around after 11 years, it's quite magnificent for me."