The odds on the Williams surname being engraved on the Venus Rosewater dish shortened further after comfortable victories for both Serena and Venus took them into the quarter finals and two more top seeds fell. Defending champion Venus beat Alisa Kleybanova in straight sets while younger sister Serena coasted into the last eight after a 6-3 6-3 defeat of countrywoman Bethanie Mattek.

The chances of the first all-Williams final since 2003 was also boosted by the elimination of No.2 seed Jelena Jankovic and No.4 seed Svetlana Kuznetsova. Kuznetsova was beaten 6-4, 1-6, 7-5 by 19-year-old Pole Agnieszka Radwanska in a match lasting two hours four minutes. Jankovic's straight sets loss to Tamarine Tanasugarn earlier in the day meant all four top seeds have now exited the tournament. Jankovic's defeat follows the elimination of No.3 seed Maria Sharapova and Ana Ivanovic, the No.1 seed.

Jankovic lost in straight sets to the Thai player but was severely hindered by a knee injury sustained in the previous round victory over Caroline Wozniacki. On Sunday, the Serb received constant treatment on the problem, diagnosed as a meniscus tear, and it was touch and go whether she would be able to play.

In the end, she succumbed in straight sets, 6-3 6-2, and expressed her frustration at the early scheduling of her match, which started at 12pm on Court 18. "I asked to play a little bit later on in the day, which would have given me a few more hours to recover and do another therapy in the morning. When I saw I was scheduled to play at 12pm, especially on Court 18, I thought it was very unusual for a No.2 seed."

Defending champion Williams senior was scheduled for Court Two, another decision Jankovic considered strange. The two women's matches on the show courts involved lower-ranked players - Kuzentsova against Radwanska on Centre and Nicole Vaidisova against Anna Chakvetadze on Court One.

"I think the No.1 and No.2 seeds should always be on these top show courts," said Jankovic. "I don't know what they are doing putting Venus on No.2 and me on No.18, especially with me having an injury and asking for a favour to play a little later on.

"I was almost playing in the parking lot. I almost needed a helicopter to go to my court. They told me Court 18 is a TV court and I told them so were Centre and No.1."

Williams senior was more restrained, but clearly not happy while her younger sister, who followed her onto Court Two, also expressed dismay about the scheduling. "I thought it was weird to have a four times defending champion on there. I've only won it twice," smiled Serena, who plays Radwanska in the last eight. "Initially, I thought, Is this the right schedule?' but I didn't dwell on it. It gave me extra motivation to win."

Williams senior booked her passage in perfunctory fashion by overcoming Kleybanova in straight sets. The defending champion has grown into the tournament impressively and has yet to drop a set. She never looked in any danger against the Russian teenager and will now play Tanasugarn in her ninth appearance in the last eight at Wimbledon.

The 28-year-old has not lost a set against Tanasugarn in half a dozen previous meetings. "She's playing well her and she has marched through," said Williams. "I haven't seen her play this year, but I have played her a number of times. I think I'll be more prepared as far as knowing how my opponent plays than my first four opponents. That makes it a little bit easier."

Jie Zheng, the Chinese wildcard, continued her remarkable journey by knocking out her third seed of the tournament, Hungary's Agnes Szavay. The 24-year-old, who beat Ivanovic in the previous round and Slovakia's Dominika Cibulkova in the first round, won 6-3, 6-4, and has yet to drop a set in her four matches. She will play Vaidisova in the last eight, who beat Chakvetadze.

Nadia Petrova, the No.21 seed, is safely through to her first quarter-finals since the Australian Open in 2006 after easing past fellow Russian Alla Kudryavtseva 6-1, 6-4. Kudryavts eva produced one of the shocks of the tournament by knocking out Sharapova, but was out-classed by her older opponent and will now face Elena Dementieva.