Date: 22 June - 5 July
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Tennis on the BBC
Venus and Serena Williams are hoping to meet in a fourth Wimbledon final
By Piers Newbery
BBC Sport at Wimbledon
Venus and Serena Williams are expected to take another step towards a repeat of last year's final with quarter-final victories at Wimbledon on Tuesday.
The American sisters have shared seven of the last nine titles and met in the final three times.
Five-time and defending champion Venus plays 11th seed Agnieszka Radwanska in the first Court One match at 1300 BST.
Two-time champion Serena plays eighth seed Victoria Azarenka second on Centre Court in arguably the match of the day.
Surprise quarter-finalist Sabine Lisicki of Germany, the world number 41, takes on world number oneDinara Safina in the opening match on Centre Court at 1300 BST.
Fourth seed Elena Dementieva plays Italy's Francesca Schiavone, the world number 43, in the second match on Court One.
Azarenka has been the biggest breakthrough star of the women's game in 2009, collecting three titles including a victory over Serena in the final in Miami in March.
If she's playing good tennis and she has a good day, it's very tough to play against her
The 19-year-old from Belarus was also giving Serena a tough time before having to retire in the second set of their Australian Open fourth-round match in January.
"She's obviously a good player and she's really young," said Serena. "She has nothing to lose. This is Wimbledon. You know, I feel the same way. It will be a really good match."
The 2002 and 2003 champion added: "I feel like I definitely need to step it up, play better, really start playing some great tennis or go home. And I don't want to go home, so I feel like I'm just getting more serious."
Azarenka said: "It's the quarter-finals, it's a big match. It's going to be loud in the big stadium and everything.
"I just have to be the same focused as I was all of these days and just keep playing my game, not to worry about that I'm playing Serena in the quarter-finals."
Venus has looked untroubled on her way into the last 16 and she benefited from the retirement of Ana Ivanovic in her last match.
Poland's Radwanska, 20, won her first match against Venus three years ago but has lost the last three, including a heavy defeat in Rome earlier this year.
"She's obviously very talented," said Venus. "She plays a different style game, but is very effective at it. Apparently she likes this surface. But I'll continue with my methods."
Radwanska is not surprised to be playing the five-time champion.
"If I'm playing quarter-finals of a Grand Slam, it's either Venus, Serena or Kuzy (Kuznetsova), so I'm not surprised," she said. "I have nothing to lose. She's a great champion here and I will try my best here again.
"If she's playing good tennis and she has a good day, it's very tough to play against her. Especially the serves, you know, she's hitting hard."
Lisicki lost to Safina in the first round of last year's Australian Open but the 19-year-old German has come on in leaps and bounds since then, taking her first title in Charleston recently and rising to 41 in the world.
"For me it's just one match at a time," she said. "I was very happy to have beaten Svetlana. I just fought for that match. I was very happy with the result.
"Getting into the second week, I just thought, you know, I have nothing to lose now. I'm playing my best tennis so far and I'm very happy, and I think I can still get much better.
"You know, I'm looking forward to the next matches."
Dementieva, a semi-finalist last year, has a 4-4 record against 29-year-old Schiavone and knows what to expect.
"I know Francesca very well," said the Russian. "I used to play junior competition with her. I think it will be tough match.
"She has a good grass-court game, she has a good slice, she has some tricky shots with her forehand, and she's aggressive with her serve."