Venus Williams is firmly behind sister Serena in her bid to become a six-time Wimbledon champion and edge ahead in their sibling rivalry.

The game-changing Americans have each lifted the Venus Rosewater Dish five times, and with Venus eliminated in a thrilling Centre Court clash with Petra Kvitova on Friday it has been left to Serena to fly the flag for tennis' most venerated family.

After a battle spanning two-and-a-half hours, Kvitova broke serve for the first time in the match to earn a 5-7 7-6 (7/2) 7-5 victory over Venus and reach the fourth round.

It shattered hopes Venus had of reaching the second week of the tournament for the first time since 2011 in the singles event.

"It's a shame there had to be a loser in this match and more of a shame that it had to be me," the 34-year-old said.

As well as playing in the doubles with Serena, Venus is backing her younger sister to carry off the singles title next Saturday.

"Well, I'm fighting with her. I'm in the stand and rocking back and forth, almost hitting the ball. I'm pretty much right there with her fighting," Venus said.

"Obviously my perspective's a little bit different than most other people's."

Top seed Serena faces a third-round clash with France's Alize Cornet on Saturday. Cornet defeated Serena in the Dubai semi-finals in February, but Venus restored family honour by thrashing the 24-year-old from Nice in the final.

If all the moons align it could be close, but given Serena dropped just five games over the first two rounds it could equally be over very quickly.

Cornet might take inspiration from Czech player Barbora Zahlavova Strycova who on Friday caused the biggest shock of Wimbledon so far by sending Chinese second seed Li Na crashing out.

She clinched a 7-6 (7/5) 7-6 (7/5) win on Court One, with Li double-faulting on match point.

Caroline Wozniacki reached the fourth round at Wimbledon for the first time in three years by ending the run of 16-year-old Ana Konjuh, and she plays Strycova next.

Following a very public split from former fiance Rory McIlroy, after wedding invitations had been posted out, and a first-round defeat at the French Open, Wozniacki headed to Miami for a holiday with Serena Williams.

The break seems to have done her the world of good. Wozniacki is always a crowd favourite but insisted she does not need the sympathy vote.

She said: " 'I think everyone here wants to make me a victim. I'm not a victim. I'm just playing tennis. I'm going about my life. I'm playing well. I'm in the second week."

French Open runner-up Simona Halep edged through a second-round tussle with Lesia Tsurenko in three sets and was due back in action on Saturday, taking on Belinda Bencic for a place in the last 16. Bencic, 17, won the Wimbledon girls' singles title last year.

Elsewhere on Saturday, unseeded American Alison Riske was next in line for Russian Maria Sharapova, with the French Open champion and fifth seed aiming to stay on course for a possible quarter-final clash with Serena Williams.