Serena Williams withdrew from the Sony Ericsson Championships on Thursday after being forced to retire from a match the previous day against Anna Chakvetadze with a left knee injury. The fifth-ranked Williams had lost the first set 6-4 in Wednesday’s match before having an MRI scan. It’s the same knee that underwent surgery in 2003 and also forced her to miss 10 tournaments last year.

Former champion David Nalbandian will not travel to the Masters Cup in China as the first alternate because it’s too far away. Nalbandian beat Roger Federer and Rafael Nadal twice each en route to Masters Series victories in Madrid and Paris in the last three weeks, and missed out on the eight-man season-ending ATP championships by 11 points.

The International Tennis Federation is investigating allegations that Tommy Haas was poisoned before Germany’s Davis Cup match against Russia. Haas was forced out of his match against Mikhail Youzhny with a suspected stomach virus. Russia won both reverse singles matches on Sept. 23 to win the semifinal series 3-2 and reach the Davis Cup final.

With her ailing shoulder out of mind, Maria Sharapova just about played like her usual self. The sixth-ranked Russian won her first match in more than two months Tuesday at the Sony Ericsson Championships, grinding out a 6-4, 7-5 win against Daniela Hantuchova. An ongoing shoulder injury had limited Sharapova to a single match since her Aug.

American twins Bob and Mike Bryan pulled out of next week’s Tennis Masters Cup doubles tournament because Mike has an elbow injury. The Bryans, members of the U.S. Davis Cup team, are the world’s No. 1-ranked doubles pair. They’ll be replaced in the field by Israel’s Jonathan Erlich and Andy Ram. “I am extremely disappointed that I won’t be able to compete in the Tennis Masters Cup this year,” Mike…

Justin Henin might not defend her Olympic gold medal in Beijing because of concern the city’s air pollution will trigger her asthma. Henin withdrew from the China Open in September because of her asthma and is worried she might be forced to skip the Beijing Games next August. “I’ve had asthma for a few months now and I felt very bad in New York at the end of the (U.S.

Serena Williams looked at her draw for the season-ending Sony Ericsson Championships and was pleased to see top-ranked Justine Henin in her difficult group. Williams has lost three straight matches against Henin since she beat the Belgian star to win the Miami Masters title in April. Henin knocked Williams out of the French Open, Wimbledon and the U.S.

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Martina Hingis said Thursday she has been accused of testing positive for cocaine at Wimbledon, and then announced her retirement from professional tennis. Hingis, a five-time Grand Slam champion and former Wimbledon winner, denied using cocaine. “I find this accusation so horrendous, so monstrous that I’ve decided to confront it head on by talking to the press,” she said.

The head of men’s tennis would ban players for life if they are caught match-fixing, but would give a second chance to players who had doped. ATP president Etienne de Villiers told a sports business conference in London on Thursday that tennis was being threatened by match fixing and gambling syndicates.