ESPN Wimbledon 2008

WIMBLEDON, England -- They are sisters and best friends, and share a flat just a few blocks from the bustling center of Wimbledon Village.

Venus and Serena Williams already have lived fortuitous lives, but nine days into this glorious fortnight, they are leading truly charmed existences. The sisters are one match each from their 16th career meeting and their seventh with a Grand Slam title on the line.

On Tuesday, their leisurely stroll through the Wimbledon field continued into the semifinals. First, Venus overwhelmed Tamarine Tanasugarn 6-4, 6-3, and then, Serena devoured Agnieszka Radwanska 6-4, 6-0. Going in, Serena's match against Radwanska was thought to be the most appetizing of the day, but the No. 14-ranked player in the world lasted only 51 minutes.

The planets have aligned quite nicely, indeed.

Kim Clijsters retired last year, and fellow Belgian Justine Henin joined her before this year's French Open. Maria Sharapova and Ana Ivanovic were among the top four seeds who left the building before the quarters. Venus has won all 10 of the sets she has played, and the average ranking of her five opponents has been a pedestrian 98th. Serena, too, hasn't dropped a set, while her average opponent ranking (68th) has been only moderately tougher.

In short, they are crushing lesser players. At Wimbledon, where holding serve means holding court, the Sisters Williams fired 19 aces Tuesday -- versus zero by their opponents.

The only thing that has hampered Venus' effectiveness is the curious lack of stormy weather. With not a stitch of cloud cover, it hit 81 degrees Tuesday.

"I've never had to serve in the sun at this tournament," Venus said. "I've played every day at noon or 1, and it's always cloudy. I can't see the ball after I serve. I'm blinded, so it's pretty interesting."

Based on the evidence supplied by the other two quarterfinals, the Williams sisters have no reason to fear Thursday's semifinal opponents. Mental picture: Food for the lions.

Elena Dementieva, who draws Venus, and Zheng Jie, Serena's next potential victim, both went three sets and played less-than-inspiring tennis in their most recent matches. Dementieva outlasted Nadia Petrova 6-1, 6-7 (6), 6-3, while Zheng handled Nicole Vaidisova 6-2, 5-7, 6-1.

Dementieva, the human nerve ending, barely survived her match with Petrova, a fellow Russian she has been playing professionally for 11 years now. Dementieva was leading 6-1, 5-1, and somehow almost managed to lose.

She went from brilliant to dodgy in about six seconds. Tightening perceptibly, she lost five straight games, then wasted two match points in the tiebreaker before succumbing 8-6.

"I was like, 'Oops, I did it again; I'm out of the semifinals,'" Dementieva said. "What can you think about it? And then when I took some time to change my dress, I was like, 'I don't want to lose.'"

Petrova, no stranger to mental anguish, staged her own meltdown in the third set. She finished with 43 unforced errors, leading to a series of self-admonishing episodes. The best moment of the match came when Petrova slammed her racket into the grass and it bounced up, grazing her face and knocking the visor off her head.

Dementieva has an uncomfortable history with big moments. True, she's reached two Grand Slam finals -- Roland Garros and the U.S. Open in 2004 -- and this will be her fifth major semifinal. However, it will be her first since the 2005 U.S. Open. And when the going gets tough, Dementieva gets … well, nervous to a fault.

In her first Grand Slam final, at that 2004 French Open, she was destroyed by Anastasia Myskina 6-1, 6-2. She fell to another Russian, Svetlana Kuznetsova, in straight sets later that year in New York. In the quarterfinals this year at Roland Garros, Dementieva was up a set and 5-2 on Dinara Safina, but she squandered a match point and wound up losing 6-4, 6-7 (5), 0-6.

Venus is 5-2 against Dementieva in her career, although they never have played on grass and have met only once in the past three years. Dementieva is actually the highest remaining seed, at No. 5.

How will she attempt to beat Venus?

"Well, just give me some time," Dementieva said. "I need to enjoy my moment. It's my first semifinals here, and I'm just very excited about it."

Zheng is the accidental tourist in the semifinals. She had never been to a major quarterfinal. On Tuesday, the 24-year-old from Chengdu, Sichuan, became the first Chinese player of any gender to reach a Grand Slam semifinal.

Vaidisova, still only 19, already has reached that threshold twice. Coming into Wimbledon, she had failed to win more than three matches in a row in 2008. But sure enough, she ripped off four victories here with her big service game and forehand, and was favored by most to advance past Zheng, who stands only 5-foot-4.

But Vaidisova digressed to her recent form in the third set; she had 18 unforced errors in that frame, the same number Zheng produced the entire match.

Zheng and Dementieva are monstrous underdogs. The Williams sisters have 14 Grand Slam singles trophies at home; Dementieva and Zheng have a total of zero.

There have been some awkward moments in the Venus-Serena catalog, particularly during the Serena Slam of 2002-03. But when they played each other in Bangalore, India, back in March, Serena won a spirited match 6-3, 3-6, 7-6 (4).

At the moment, Venus is favored to win the tournament, slightly ahead of Serena. Does Serena consider Venus the favorite?

"I would never sit here and say she's the favorite when I'm still in the draw," Serena said sharply to the reporter who asked the question. "What are you on?"

One thing you can bank on: The rest of the tennis world will be talking more about this impending matchup than the participants themselves.

"No," Venus said, "because we don't really talk about tennis a lot. The most we talk about tennis is when we're on the doubles court. We discuss the strategy and pump each other up.

"But, no. We just have to play the best tennis to deserve it, so our aim is just to play better than our opponents and really deserve to be there."

Greg Garber is a senior writer for ESPN.com.