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Tertius Pickard, Associated Press
Daniela Hantuchova of Slovakia plays a shot in her semi final match against Kim Clijsters of Belgium during the Brisbane International tennis tournament in Brisbane, Australia, Friday, Jan. 6, 2012.

BRISBANE, Australia — Australian Open champion Kim Clijsters became the second top contender for the year's first major to suffer an injury setback when she retired Friday from her Brisbane International semifinal against Daniela Hantuchova.

Clijsters won the opening set 7-6 (4), but surrendered a break at the start of the second set and needed treatment after the third game. She came back on court for one game before walking to the net and telling Hantuchova she couldn't continue after falling behind 3-1.

Hantuchova has had an abbreviated run into Saturday's final, getting a walkover in the quarterfinals when 13-time Grand Slam winner Serena Williams withdrew from the tournament after injuring her left ankle while winning a second-round match.

No. 24-ranked Hantuchova will be aiming for her fifth WTA Tour title when she plays No. 34-ranked Kaia Kanepi of Estonia, who took less than an hour to beat 2010 French Open winner Francesca Schiavone of Italy 6-3, 6-0 in the other semifinal. The third-seeded Schiavone complained of a stomach upset after the match.

Both Clijsters and Williams, the 2010 Australian Open champion, were playing their first tournaments in four months.

The top two seeded players tumbled early in the women's draw, with U.S. Open champion Sam Stosur ousted in the second round and No. 2 Andrea Petkovic losing to Kanepi in the quarterfinals.

Clijsters struggled with injuries last season and only played eight tournaments, including the win at the Australian Open that helped her return to the No. 1 ranking for one week.

The Brisbane International was her first tournament since an abdominal injury ended her season in September and the latest setback casts doubt on her ability to defend her title at the first major of 2012. The Australian Open starts on Jan. 16 in Melbourne.

She said her hip had started to go into spasms during the match and she withdrew to avoid a more serious injury.

"I felt my left hip was getting tighter and tighter to the point I couldn't move forward with my upper body," she said. "So it was the smartest choice to try and not let it get any worse, to be ready for Melbourne."

The 28-year-old Clijsters, who has won three Grand Slam singles titles since returning from time off to have a baby in 2008, was hoping tests Saturday would clear her to compete in Melbourne.

"With my stomach muscle, I knew straight away it was going to take long. With this one, I kind of have an OK feeling," she said. "If everything comes out OK tomorrow, it should take a little under a week to get completely healed. That's what I'm obviously hoping for and aiming for."

In the men's quarterfinals, top-seeded Andy Murray shifted up a gear to beat Marcos Baghdatis 6-2, 6-2.

Murray dropped the opening sets in his first two rounds as he overcame soreness and stiffness from the offseason, but had no serious difficulty dispatching doubles partner Baghdatis in little more than an hour.

Murray has lost the last two Australian Open finals and recently hired Ivan Lendl to help him break his Grand Slam title drought. The Scot will next play eighth-seeded Bernard Tomic.

The Australian teenager, a quarterfinalist at Wimbledon last year, converted the only breakpoint chance of the match to beat Uzbekistan's Dennis Istomin 6-3, 7-6 (4).

Murray saved both break points he faced against Baghdatis, the 2006 Australian Open runner-up, and converted all four of his own.

After a difficult service game to hold in the fourth game of the second set, Murray broke in the fifth to take a 3-2 lead.

He earned triple breakpoint two games later after a scrambling rally that included a shot between his legs that caught Baghdatis off guard. Murray secured a 5-2 lead on the next point when he successfully challenged a baseline call.

"I played very well today ... moved very well from the start, which wasn't the case in the last two matches, so really, really happy," Murray said. "The aches and pains I had from the first two matches have gone, so it's good."

Murray has lost three major finals, and is desperate to end a drought for British men in Grand Slam singles that dates to 1936. Lendl, an eight-time Grand Slam titlist, arrived in Australia from the United States on Friday and was due to meet with Murray in Brisbane on Saturday to start fine-tuning for the Australian Open, which starts Jan. 16 in Melbourne.

"The Australian Open has always been the tournament that I've done my best at since I was young," said Murray, who has overcome the groin strain that curtailed the end of his 2011 season. "So I look forward to going back there and hopefully go one better than last year."

The No. 42-ranked Tomic has played Novak Djokovic, Roger Federer and Rafael Nadal, so has a good idea of what to expect from No. 4-ranked Murray in the semifinals.

"Tomorrow will be a test for me to see where I am," he said. "I am ready. I know I can take sets off these guys. In a best-of-three match like this ... maybe I can pull off a win."

In women's semifinals, Australian Open champion Kim Clijsters was playing Daniela Hantuchova, who got a walkover in the quarterfinals when 13-time Grand Slam winner Serena Williams withdrew from the tournament after injuring her left ankle, and Francesca Schiavone takes on Estonia's Kaia Kanepi.