Andy Roddick wasn’t “losing sleep” about an illness that will cause defending champion Roger Federer to miss his normal tuneup for the Australian Open. Federer had a serious stomach virus over the weekend and withdrew from the Kooyong exhibition tournament, where he usually prepares for the first Grand Slam event of the season.

Mario Ancic could miss next week’s Australian Open because of a stomach illness that forced him to withdraw Tuesday from his first-round match at the Heineken Open. The Croatian, who also withdrew from last week’s Adelaide International because of illness, did not play his scheduled match with Spain’s Juan Carlos Ferrero.

Roger Federer has a severe stomach virus and has pulled out of an exhibition tournament less than a week away from the Australian Open. Federer told officials at the Kooyong Classic on Monday that he became ill after arriving in Australia last Friday from his training base in Dubai. “It continued to get worse over the weekend,” the top-ranked Federer said.

Ninth-ranked Daniela Hantuchova pulled out of the JB Group Classic Hong Kong exhibition tournament due to abdominal pains on Friday. The withdrawal diminishes Hantuchova’s preparation for the Australian Open, scheduled for Jan. 14-27. Hantuchova first withdrew from the doubles competition Thursday then pulled out of the singles the following day.

Defending champion Xavier Malisse and fourth-seeded Mikhail Youzhny posted second-round wins Wednesday to set up a quarterfinal encounter in the Chennai Open. Malisse, a Belgian, beat sixth-seeded Jurgen Melzer of Austria 7-6 (3), 6-2, and Youzhny, a Russian, held off Frenchman Edouard Roger-Vasselin 7-5, 1-6, 6-2.

Maria Sharapova beat 17-year-old Caroline Wozniacki of Denmark 6-2, 6-2 Wednesday to reach the semifinals of the JB Group Classic exhibition. Sharapova, ranked No. 5, was playing her second match of the year. She missed nearly two months last season because of a shoulder injury, but the former Wimbledon and the U.S.

Australian wild-card Joseph Sirianni advanced to his first ATP Tour quarterfinal, beating American Sam Querrey 6-7 (5), 6-2, 6-3 on Wednesday in the Australian men’s hardcourt championships. The 32-year-old Sirianni, ranked 195th, broke Querrey’s serve to take a 4-2 lead in the deciding set. Serving for the match, Sirianni fell behind 0-40 before recovering to win in just under 2 hours.