Chinese second seed Li Na suffered a shock third round exit at Wimbledon after going down 7-6(5) 7-6(5) to the Czech Republic's Barbora Zahlavova Strycova.

The Australian Open champion has never felt comfortable on the slick lawns of the All England Club, with her best showing being three quarter-final appearances in eight visits.

She is the highest seed to fall so far at this year's championships.

Strycova will tackle Denmark's former world number one 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," she said.

"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 ended the run of 16-year-old Ana Konjuh to reach the fourth round for the first time in three years.

Konjuh came through qualifying and won two rounds at a grand slam for the first time but found Wozniacki's experience and guile far too much as the Danish 16th seed triumphed 6-3 6-0.

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 fine 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 dropped just 11 games in three matches and could next meet second seed Li Na.

French Open runner-up Simona Halep presented a confusing account of her grass-court credentials as she mixed the brilliant with the distinctly average in a second-round win over Lesia Tsurenko.

Romanian Halep is the third seed after a stunning 13-month run on tour, in which she has won seven tournaments to sprint into the world's top five.

And at times on Court Two against Ukrainian Tsurenko she lived up to her billing as the break-out star of the women's tour, but come the final point a 6-3 4-6 6-4 victory was a relief, with Halep punching the air in delight at getting the job done.