MELBOURNE, Jan 27: Australia’s brutal January weather claimed another victim on Tuesday when defending champion Novak Djokovic quit midway through his Australian Open quarter-final against Andy Roddick.

“Aussie Jelena” Dokic was given every chance to again thrill home fans having been scheduled on the cool night session, but her dream run ended 6-4, 4-6, 6-4 at the hands of Dinara Safina.Roger Federer compensated the night crowd with a short but extremely sweet performance, however, smashing eighth seed Juan Martin del Potro 6-3, 6-0, 6-0.

“Things went much better than I expected,” the 13-time Grand Slam winner said. “So surprising to have a score like that in the quarters of a slam,” he added after the 80-minute tennis lesson.

Wilting Serb Djokovic became increasingly distressed as temperatures on court soared above 40 degrees Celsius before becoming the fourth player in 24 hours to abandon his match.

“Cramping and soreness in the whole body,” the world number three said when asked why he had quit while trailing 6-7, 6-4, 6-2, 2-1.

“Really unfortunate way to end up my Australian Open 2009 here in this way. Really tried my best, but sometimes you can’t fight against your own body.”

Roddick kept his focus.

“I’m probably the least favoured of anybody to make it to the semis here,” he said. “I’m just going to keep going and keep my head down and keep working. I’m not going to get too excited.”

Dokic’s emotionally-charged run at Melbourne Park had captured the imagination of her adopted homeland but her luck finally ran out against the in-form Safina.

The third-seeded Russian advanced to her third grand slam semi-final in eight months and stayed on course to emulate big brother Marat Safin by winning the Australian Open.

“I’m so sorry for beating [an] Australian tonight,” Safina told the crowd during a courtside interview. “I hope you will be behind me next time.”

Dokic, who is ranked 187th in the world and beat three seeded players just to get to the quarter-finals, remained upbeat.

“Of course I’m disappointed,” she said. “But there are more positives than negatives. It’s been a great start to 2009, I couldn’t have asked for anything more.”

Safina next meets fellow Russian and seventh seed Vera Zvonareva after she eased into the women’s semi-finals with victory over Marion Bartoli.

The Frenchwoman also wilted during the 6-3, 6-0 thrashing.

“I have to say it was definitely some tough conditions,” she told reporters. It was really hot.”

The temperature dropped for the evening session but second-seed Federer was white-hot in his thrashing of del Potro.

The Argentine won just eight points in the second set and six in the third as the 27-year-old Federer advanced to his 19th successive Grand Slam semi-final.

“I can’t do nothing in the match,” a stunned del Potro said.

Federer was equally surprised.

“I thought it was going to be a tough match in the beginning. We had some tough rallies... I was very mistaken. I’m happy about that,” he smiled.

“I guess it’s kind of what happens sometimes. You always play better against the better ranked players because they push you more and you push yourself more.”

Djokovic’s withdrawal came 24 hours after almost half Monday’s field had reached the quarter-finals when their opponents retired injured or ill.

Serena Williams, Svetlana Kuznetsova and Gilles Simon all eased into to the last eight of their draws without having to complete their matches.

Gael Monfils and Zheng Jie waved Simon and Kuznetsova through by pulling out with wrist injures while women’s second seed Williams advanced when Victoria Azarenka staggered off centre court in tears, off-balance and barely able to hold her racket, a victim of a virus and the heat.

Melbourne is braced for its hottest week in 100 years as meteorologists predict five consecutive days above 40 for the first time since 1908.

Tournament officials can halt matches if their “heat stress index” reaches a predetermined level. The index is a combined measurement of temperature, heat radiation, wind, and humidity.

When the EHP has been operational in the past, the temperature has been above 38 degrees. Organisers said the temperature was 37.1 degrees Celsius when Djokovic quit.

On-court temperatures are generally up to 10 degrees hotter than the off-court figure and photographers courtside have been covering themselves with towels after being burnt through their clothes.

Tuesday’s results (prefix number denotes seeding):

Men’s singles:

Quarter-finals: 2-Roger Federer (Switzerland) bt 8-Juan Martin del Potro (Argentina) 6-3, 6-0, 6-0; 7-Andy Roddick (US) bt 3-Novak Djokovic (Serbia) 6-7 (3-7), 6-4, 6-2, 2-1 – Djokovic retired.

Women’s singles:

Quarter-finals: 3-Dinara Safina (Russia) bt Jelena Dokic (Australia) 6-4, 4-6, 6-4; 7-Vera Zvonareva (Russia) bt 16-Marion Bartoli (France) 6-3, 6-0.—Reuters