WIMBLEDON, England — One prematch glance yesterday at the data displayed on those fancy, new digital scoreboards at staid, old Wimbledon provided a pretty persuasive case for why Venus Williams might be considered the woman to beat.

The entry under career record at the grass-court Grand Slam: "55-7." The listing of her best result: "WINNER 2007, 2005, 2001, 2000."

Yet another reason to like the American's chances: The way she served during the ensuing 6-4, 6-3 quarterfinal victory over Tamarine Tanasugarn — smacking eight aces, saving nine of the 10 break points, tying her Wimbledon record with a 127 mph delivery.

That extended Williams' winning streak at the All England Club to 12 matches, including 19 sets in a row. Nonetheless, at least one person who knows a thing or two about tennis and a thing or two about Venus Williams flatly rejected the notion that she's the favorite: Serena Williams.

Asked after her own impressive quarterfinal victory — 6-4, 6-0 against 11th-ranked Agnieszka Radwanska — whether her older sister should be considered the likeliest champion, Serena shot back: "I would never sit here and say she's the favorite when I'm still in the draw. What are you on?"

Rather than a sibling rivalry, that response perhaps reflects nothing more than the sort of competitive drive that helped the younger Williams win eight Grand Slam singles titles. That haul includes the 2002 and 2003 Wimbledon championships, each time concluded with a win over her sister.

One more win apiece, and they'll reprise the all-in-the-family final tradition Saturday. In tomorrow's semifinals, Serena will face 133rd-ranked Zheng Jie, who became the first Chinese player to reach the semifinals at a major tournament by upsetting 18th-seeded Nicole Vaidisova, 6-2, 5-7, 6-1.

Venus next plays the highest-seeded remaining woman, No. 5 Elena Dementieva, who beat No. 21 Nadia Petrova, 6-1, 6-7 (6), 6-3.

Zheng is the first wild-card entrant to reach the women's semifinals at Wimbledon; only one woman ranked lower has made the semifinals at any Grand Slam.

"I just try my best to keep going," Zheng said.

"China has quite a lot of sports in which it is a world leader," she said through a translator. "Unfortunately, tennis is not one of them."

Like Zheng, Radwanska and Tanasugarn were playing in the Wimbledon quarterfinals for the first time. Unlike her, they were forced to deal with a Williams yesterday.

More specifically, they were forced to deal with those Williams serves, developed by Dad all those years ago on the courts in Compton, Calif.

"We're different," Venus said. "I serve big almost every time. She goes for a little more placement."

Against Radwanska, Serena hit 11 aces, including four in one game while pulling even at 3-3 in the first set. On the last of those, Radwanska lunged and whiffed, then grimaced at her racket.

"It's too much, you know," Radwanska said.

She isn't exactly a nobody, having won the Wimbledon junior title in 2005 and pulled off an upset of defending champion Maria Sharapova at last year's U.S. Open. But Serena made her look absolutely ordinary, if that, taking 28 of the last 37 points.

While Serena mixed 120 mph serves with spinning, kicking changeups, Venus stuck with the hard stuff against Tanasugarn.

"I have a lot of power, so it helps," Venus said. "Definitely, the power helps."

She produced some of her best stuff when she needed to, particularly in the match's sixth game.

Tanasugarn earned six break points, and the first five vanished thanks to, in order, a 107 mph service winner, a 102 mph service winner, a 115 mph service winner, a 94 mph service winner and a 122 mph ace.

"I'm really blessed to be able to have a serve to get me out of those issues," Venus said.

On break point No. 6, Tanasugarn managed to put her return in play but then slapped a forehand into the net.

That's when she turned her back to the court and motioned toward the players' guest box with her hand, raising one finger at a time to count out those missed opportunities: 1-2-3-4-5-6.

"She served very well during the break points," Tanasugarn said. "So what can I do?"

A few moments later, she did come up with a possible solution. A tad envious of her statuesque opponent — the 6-foot-1 Williams has 8 inches on her — Tanasugarn said, "Next life, I want to be tall as her. Please."

Neither Williams has dropped a set during the tournament, and their seedings — Serena is No. 6, Venus No. 7 — certainly seem to have been miscalculated. It's the first time at any Grand Slam in the 40-year Open era that none of the four top-seeded women reached the quarterfinals, making the path even smoother for the siblings.

Hard to believe, but there hasn't been a Williams vs. Williams final at a tournament since 2003 at the All England Club.

And what if they do meet again for the title, in what would be their seventh matchup in a Grand Slam final? What would breakfast be like Saturday morning at the place they're sharing here?

"I'm going to sabotage her and eat all the breakfast," Serena said. "I'll eat all the Wheaties so she doesn't have any chance."