Sharapova was overwhelmed by Williams' brutal power-hitting when they last met on the All England Club grass courts in 2005. The Russian crumbled in the second set of that semifinal and would love the chance to get revenge this year.

On Saturday, Sharapova eased into the last 16 with a 6-3, 6-3 over Japan's Ai Sugiyama and will face Williams if the three-time Wimbledon winner beats Akiko Morigami.

The American was a set up on Morigami when rain forced a suspension.

With a potential clash of the former champions on the cards, Sharapova, who won the title in 2004, is adamant she has learned from that defeat two years ago.

"I felt like at that stage in my career I wasn't really ready," Sharapova said.

"She played really good tennis and I didn't think that I was capable of playing the same tennis for two or three sets. I was down in the first, then when I got back my level really dropped.

"It wasn't so much a wake-up call. I've always known there was so much room for improvement physically for me, but it was also the intensity level of putting two games together, breaking her and keeping that intensity after you break your opponent, being smart about things.

"Sometimes I felt like I was going for a little too much when I didn't have to. Against someone like her, you don't get away with it as much. That's something that I've improved."

The world number two won her last match against Williams, on the hard courts in Miami this year, but admits that victory will count for nothing if they meet again at Wimbledon.

"If I play her, we always have really, really tough matches but it's a Grand Slam and you try to bring up the intensity with every match," she said.

"You can never really underestimate her as an opponent. She's a champion. She's achieved many things, won many Grand Slams. You know that when you go out against her, you always have to be at you best."

If Sharapova does face Williams, she will hope the shoulder and hamstring injuries that have troubled her for several weeks have receded.

She revealed she needs lengthy treatment every day to keep her in condition to play: "Ice, massage, strength, acupuncture work. You name it, I do it really," she said. "It takes two and a half hours a day."

Sharapova was fortunate to finish her match against Sugiyama. At match point, her Japanese opponent made it clear she wanted to go off because of the heavy rain that was falling on Court One.

Play had already been suspended on other courts but American umpire Lynn Welch tested the surface and decided to play on, giving Sharapova the chance to quickly wrap up the tie.

Sugiyama was furious with the decision and Sharapova admitted she was relieved to have won.

"It was really good to finish it because I was starting to get agitated," said the Russian.

"I saw the rain in the middle of the second set and I knew if it keeps going, obviously the grass is going to get wet. I didn't want it to be too dangerous to play out there but it worked out well in the end."