Even Roger Federer, who knows a thing or two himself about success at the grass-court Grand Slam tournament.

"It seems when they're playing well," Federer observed, "that there's not much of a chance for the other girls."

That is true, particularly when it comes to Wimbledon, where recent records and the rankings don't seem to have any bearing on how the Williams sisters will fare. Remember: Serena Williams showed up at the All England Club with a 4-5 record since early April. Her older sibling Venus was not much better in that span, going 6-5.

Both trail No. 1 Dinara Safina in the rankings.

And yet, if No. 2 Serena beats No. 4 Elena Dementieva in Thursday's semifinals, and No. 3 Venus gets past Safina, they would set up the fourth all-Williams title match at Wimbledon and second in a row. As it is, one Williams or the other has won seven of the past nine championships here.

"I mean, it's been quite incredible what Venus has been able to do here at Wimbledon also, winning five times, just being so consistent for so many years," Federer said. "Serena obviously having won the career Grand Slam already since a long time has always been one of the biggest contenders for any major in the last few years. I like to watch them because they're very powerful."

Yes, there is little doubt who is expected to meet in Saturday's final.

"You never know what could happen," said eighth-seeded Victoria Azarenka, who lost to Serena 6-2, 6-3 in the quarterfinals, "but I'm pretty sure they're playing very good tennis, and they deserve to play in the final."

It's the first time the top four-seeded women all reached the semifinals at a major tournament since it happened at Wimbledon in 2006. Yet the matchups could hardly appear more lopsided.

Venus leads Safina 2-1 in previous meetings, while Serena leads Dementieva 5-3. Of more significance might be these statistics: Venus is 12-4 in Grand Slam semifinals and has seven titles, and Safina is 3-1 with zero titles; Serena is 13-2 in Grand Slam semifinals with 10 titles, and Dementieva is 2-5 with zero titles.

Venus is bidding to become the first woman since Steffi Graf in 1991-93 to win Wimbledon three years in a row and is trying for No. 6 overall. Serena beat Venus in the 2002 and 2003 finals at the All England Club.

"We have a great game. We have strong serves. I think we have pretty good returns," Serena said. "We both move pretty well. So I think that's a pretty solid game."

Should a championship match come about, they would turn into rivals. Until then, though, they are teammates.

They're sharing a house during the tournament. They practice together - an advantage no one else on tour has. And they're playing doubles as a pair, defending their Wimbledon title and reaching the semifinals by defeating Anna-Lena Groenefeld of Germany and Vania King of the United States 6-2, 7-5 Wednesday.

With Dad snapping photos from the stands, the sisters sure formed an opposing duo warming up side-by-side along the baseline. When Venus smacked an ace to end the opening game, she and Serena slapped palms.

Their interaction doesn't change much as they move closer to a possible Grand Slam final.

They are, after all, used to this: There have been seven all-Williams championship matches at majors, with Serena holding a 5-2 lead. Overall, the sisters are tied 10-10.