Na problem for Strycova

Barbora Zahlavova Strycova caused the sensation of Wimbledon so far by sending second seed Li Na crashing out in the third round.

Strycova clinched a 7-6 (7/5) 7-6 (7/5) win against China's leading sportswoman, and sealed victory amid high drama on Court One.

Strycova, the entire crowd, a line judge and the umpire thought the match was over when reigning Australian Open champion Li sent a forehand apparently long after serving at 6-5 behind, but an appeal was launched and Hawk-Eye showed it had flicked the outside extremity of the baseline.

The extra life was spurned though, with 32-year-old Li double-faulting to ensure Strycova, having gone from the euphoria of celebrations to refocusing on the replayed point, did not need to hit another ball.

With the win finally beyond doubt, Strycova walked around the court, taking in the crowd's acclaim and yelling 'come on!' before departing to another huge ovation.

Strycova will tackle Denmark's former world No 1 Caroline Wozniacki in the fourth round. For the 43rd-ranked Czech it will be a first appearance in the last 16 at Wimbledon in what is her 11th shot at success in the tournament.

"I'm very happy. I played a really good match and I enjoyed playing on Court One," said Strycova, who at the age of 28 has enlisted a sports psychologist in a late-career effort to bring a new dimension to her game.

"You have to believe in yourself and I did. I thought I could do it so I was pushing myself a lot and that's what happened."

Wozniacki had earlier ended the run of 16-year-old Ana Konjuh to reach the fourth round at Wimbledon for the first time in three years.

Croat teenager Konjuh came through qualifying and won two rounds at a grand slam for the first time as she beat Marina Erakovic and then Yanina Wickmayer earlier in the week.

However, she found Wozniacki's experience and guile far too much as the Danish 16th seed eased to a comfortable 6-3 6-0 victory in just 70 minutes.

Wozniacki has been having a miserable run at grand slams, going out before the last 16 at her last five major tournaments, but she has looked in solid form so far at the All England Club.

Konjuh's powerful hitting kept her on level terms in the early stages, but Wozniacki broke for 5-3 in the opening set and then saved a break-back point with an ace.

She found two more of those when Konjuh also had the chance to level at 1-1 in the second set, and from there the young Croatian's head went down.

Wozniacki, who has never reached the quarter-finals at Wimbledon, has now dropped only 11 games in her three matches to date.

Petra Kvitova outlasted Venus Williams 5-7 7-6 (7/2) 7-5 in a serve-dominated, third-round battle of the former champions on Centre Court.

Sixth seed Kvitova. who lifted the title in 2011, surrendered her delivery for the only time in the match to hand five-time champion Williams the opening set.

Both players remained resolute on serve throughout the second set, won 7-2 in a tie-break by Kvitova, and a solitary break of Williams' serve by the Czech left-hander in the 12th game of the decider brought the match to an end.

Kvitova fired 11 aces and 45 winners in total and will take on China's Shuai Peng in the fourth round.

Williams won the most recent of her Wimbledon titles in 2008 but, at 34, said afterwards she has no plans to quit.

"There have been people trying to retire me since I was 25," she said. "For some reason we do that in tennis to our players.

"It's weird. We don't encourage them to stick around. It's like, 'Get out of here'.

"So I'm not getting out of here. I think this year has been a great year for me. I've had some tough losses, but I've learned a lot from them. I'm finding my way back on my feet.

"I'm proud of myself for what I'm achieving on the court."

Also on Friday, world No 3 Simona Halep booked her place in the third round, although she was forced to come through a much sterner examination against Lesia Tsurenko.

Halep - who reached the final of the French Open last month - looked to be in charge having clinched the first set 6-3.

However, her Ukrainian opponent took the next to force a decider and Halep was pushed all the way before closing out a 6-3 4-6 6-4 victory.

The Romanian will now face Switzerland's Belinda Bencic who beat Amercan Victoria Duval 6-4 7-5, while 23rd seed Lucie Safarova claimed the scalp of 10th seed Dominika Cibulkova 6-4 6-2.