BRISBANE, Australia (AP) — 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 (pictured) 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.

Meanwhile Roger Federer has pulled out of his semifinal match against Jo-Wilfried Tsonga at the Qatar Open because of a back injury.

The 16-time Grand Slam champion says his back has not improved since beating Andreas Seppi in three sets on Thursday.

Rafael Nadal will meet Gael Monfils in the other semifinal match.