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Andrew Brownbill, Associated Press
Petra Kvitova of the Czech Republic wipes the sweat from her face during her fourth round match against Serbia's Ana Ivanovic at the Australian Open tennis championship, in Melbourne, Australia, Monday, Jan. 23, 2012.

MELBOURNE, Australia — Wimbledon champion Petra Kvitova recovered from an embarrassing miss and a two-game lapse to beat Ana Ivanovic 6-2, 7-6 (2) on Monday for a spot in the Australian Open quarterfinals.

Two-time Australian Open runner-up Andy Murray only spent 49 minutes on court in the next match at Rod Laver Arena and was leading 6-1, 6-1, 1-0 when Mikhail Kukushkin retired from their fourth-round match with a left hip injury, giving him an easy path into the quarterfinals.

The 21-year-old Kvitova was seemingly fast-tracking her progress to the last eight until her game momentarily came undone near the end of the second set after she missed a routine overhead at the net to allow the former French Open champion to pull to 4-5.

She lost the next eight points to fall behind 6-5 — badly missing on a couple of wild groundstrokes — and only managed to force a tiebreaker with two big serves out wide in the 12th game.

Ivanovic's two double-faults early in the tiebreaker gave Kvitova some easy points and took the pressure off.

The match seemed close to ending much earlier when Kvitova got into perfect position to put away an innocuous lob from Ivanovic, but played through the shot too quickly and was hit instead on the body.

"It was a very tough match at the end. I mean it was a really easy point then I thought I got it and I lost eight points in a row," she said. "I'm very happy I played very well in the tiebreak."

She'll next play either Sara Errani of Italy or China's Zheng Jie, a semifinalist here in 2010.

The temperature in Melbourne hit 90 degrees on Monday and the sunny conditions made it difficult to serve from one end.

"It's obviously good for me, I get to conserve some energy," Murray said. "Tough for him, first time in the fourth-round of a Slam."

Murray said he slowed down his serve to improve his accuracy, but that was more because he wanted to work an ailing Kukushkin around the court in protracted points.

"Sounds bad, but that was the tactic and it worked," said Murray, who had a narrow, three-set win over the Russian-born Kazakhstan player in a warmup tournament at Brisbane two weeks ago, but was more prepared for what to expect this time.

"I felt like I moved better — in Brisbane he came out swinging and I wasn't ready for it."

Murray, the losing Australian Open finalist the past two years, will next play either 2008 finalist Jo-Wilfried Tsonga or Kei Nishikori of Japan.

Defending champion Novak Djokovic was playing Lleyton Hewitt on Monday night, while five-time women's champion Serena Williams had an afternoon meeting with Ekaterina Makarova of Russia.

Reigning women's champion Kim Clijsters saved four match points in the second-set tiebreaker and overcame a left ankle injury to beat Li Na 4-6, 7-6 (6), 6-4 on Sunday in a rematch of last year's final.

That put the Belgian veteran on course for a quarterfinal against top-ranked Caroline Wozniacki, who had a 6-0, 7-5 win over former No. 1 Jelena Jankovic. Wozniacki is yet to win a major, but her confidence is high.

"If I play like I did today, Kim will have to really play well to beat me," she said.

Clijsters needed pain killers to get through the 2-hour, 23-minute win over Li and she's hoping ice treatment will help her recover in time for the quarterfinals.

Third-seeded Victoria Azarenka advanced with a 6-2, 6-2 win over Iveta Benesova. She next plays eighth-seeded Agnieszka Radwanska.

Roger Federer more or less held a clinic at Rod Laver Arena, where he has won four of his 16 Grand Slam titles, on Sunday night — a 6-4, 6-2, 6-2 victory over Bernard Tomic that moved him into the quarterfinals for a 31st consecutive major.

Federer mixed soft, angled drop shots that just cleared the net with crisp groundstrokes that hit the lines and — for good measure — a leaping, backhand overhead.

Federer's quarterfinal will be his 1,000th tour-level match. He plays 2009 U.S. Open champion Juan Martin del Potro, whom he once expected to rise to No. 1.

Rafael Nadal advanced with a convincing win over fellow Spaniard Feliciano Lopez. The 2009 champion's right knee was heavily wrapped and his left ankle needed to be taped after three games of the first set. Afterward, he said he was fine.

He next plays Tomas Berdych, hoping to avoid a third consecutive quarterfinal loss in Melbourne. Berdych beat Nicolas Almagro 4-6, 7-6 (5), 7-6 (3), 7-6 (2), then was jeered by the crowd at Hisense Arena after he refused to shake hands with his Spanish rival. The Czech was upset that Almagro had hit the ball straight at him while he was at the net during the fourth set.

"I think when you have a point and someone wants to hit you straight to your face, I don't see this as a nice moment," Berdych said during a post-match TV interview. "This is not the way how tennis is."