- Kim Clijsters retires from the Brisbane Open semifinals with a hip injury
- The Belgian withdrew after falling a set and a break down to Daniela Hantuchova
- Slovakian Hantuchova will play Kaia Kanepi of Estonia in Saturday's final
- Zheng Jie of China and Italy's Flavia Pennetta will meet in the final of the ASB Classic
Four-time grand slam champion Kim Clijsters withdrew from her Brisbane International semifinal with a hip injury on Friday, casting doubt over the defense of her Australian Open crown later this month.
The former world No. 1 lost the first set to Daniela Hantuchova and was 2-1 and a break down in the second against the Slovakian when she left the court for medical treatment. The Belgian returned and lost a further game before signaling to the umpire to end the match.
Clijsters admitted to feeling stiff prior to the contest and chose to retire rather than risk causing an injury which could keep her out of the Melbourne grand slam, which begins on January 16.
It was her first top-level tournament since August, when a stomach injury forced her to miss the rest of last season. Clijsters was also sidelined for significant periods earlier in 2011 by ankle and shoulder problems.
"I just felt my left hip getting tighter and tighter to the point where I felt like I couldn't go forward with my upper body or put any pressure on when I was landing on my serve," the 28-year-old told the tournament's official website.
"So it was the smartest choice to try and not let it get any worse, to be ready for Melbourne in a couple of weeks. When you feel it getting worse and worse, you almost don't have a choice."
It was the second time in as many matches that Hantuchova has benefited from an injury to her opponent.
The 28-year-old received a walkover in the quarterfinals when 13-time grand slam winner Serena Williams withdrew with an ankle problem which could force her out of the tennis season's first major.
Hantuchova will face Kaia Kanepi in Saturday's final after the Estonian beat Italy's 2010 French Open champion Francesca Schiavone 6-3 6-0.
Kanepi kept alive her hopes of a second WTA Tour title with a comprehensive win over third seed Schiavone, wrapping up victory in just 55 minutes.
Meanwhile, Wimbledon champion Petra Kvitova sent a warning to world No. 1 Caroline Wozniacki by winning their singles clash in the Hopman Cup teams event in Perth.
The second-ranked Kvitova and men's No. 7 Tomas Berdych booked the Czech Republic's place in Saturday's final against France with victories against Denmark's Wozniacki and Frederik Nielsen.
Kvitova earned a hard-fought 7-6 3-6 6-4 triumph, while Berdych cruised to a 6-1 6-3 success.
The Bulgarian pair of Grigor Dimitrov and Tsvetana Pironkova finished second in Group A above Denmark after a 2-1 win over the U.S.
Bethanie Mattek-Sands, who helped John Isner win the title last year, gave the Americans the lead by beating Tsvetana Pironkova 6-4 6-4.
But world No. 76 Grigor Dimitrov upset eighth-ranked Mardy Fish 6-2 6-1 and then the Europeans won the doubles 8-5 to leave the U.S. bottom of the table.
Richard Gasquet and Marion Bartoli qualified for the final by beating Spain on Thursday for a third successive win in Group B, and will seek to earn France's first title.
China's Zheng Jie and Flavia Pennetta of Italy will contest the final of the WTA Tour's ASB Classic in Auckland, New Zealand.
Jie battled back from a set down in her semifinal against Russian third seed and two-time grand slam champion Svetlana Kuznetsova to win 2-6 6-3 6-3.
Pennetta was a runner-up at the event in 2010 and will once again compete in the final following a 6-1 6-2 defeat of Germany's Angelique Kerber.