Allegations about match-fixing have lingered, and now Tommy Haas is undergoing further medical tests to determine if he was poisoned during Germany's Davis Cup semifinal loss to Russia in September.
The season-ending Masters Cup, with its $4.5 million purse, starts Sunday with round-robin play. The eight players are divided into two groups.
The match-fixing allegations loom over fourth-ranked Nikolay Davydenko. The investigation began after online betting exchange Betfair voided wagers because the Russian withdrew against 87th-ranked Martin Vassallo Arguello in the third set due to a foot injury in a match in Poland in August.
Davydenko was fined $2,000 by the ATP for "lack of best effort" during a 1-6, 7-5, 6-1 loss to Marin Cilic at St. Petersburg, then was jeered by the crowd -- and criticized by the chair umpire -- while committing 10 double faults in a straight-set loss to Marcos Baghdatis in Paris. Davydenko claimed his serve has abandoned him.
Other players, including Belgium's Gilles Elseneer and France's Arnaud Clement, have since claimed they turned down money to fix matches -- Elseneer claimed he was offered $100,000 to lose to Potito Starace in the first round at Wimbledon in 2005.
An unidentified German player was quoted on television this week as saying not many players are involved, but "those that do it are more professional about it than about playing tennis itself."
Haas was forced out of his Davis Cup match against Mikhail Youzhny with a suspected stomach virus as Russia won both reverse singles matches on Sept. 23 to win the semifinal series 3-2 and reach the final against the United States.
German teammate Alexander Waske said he was told by a Russian who manages numerous athletes that it was poisoning, not a virus. Waske didn't say who the manager was.
"We do not speculate but the German federation will act if there is any proof," federation president Georg von Waldenfels told The Associated Press. "I think one has to take these things seriously."
Haas, who says he continues to be bothered by the ailment, planned to fly Thursday to the U.S. for a complete checkup, and the International Tennis Federation said it is investigating.
The Italian tennis federation was looking into a report Thursday that 124th-ranked Alessio Di Mauro bet on matches.
Di Mauro's coach, Fabio Rizzo, told Gazzetta dello Sport that Di Mauro was an avid online gambler but never bet on his own matches or cheated.
MOVING ON IN MADRID
MADRID, Spain --- Maria Sharapova (above) reached the semifinals at the Sony Ericsson Championships with a 5-7, 6-2, 6-2 win Thursday over second-ranked Svetlana Kuznetsova.
The sixth-ranked Russian pulled away by breaking Kuznetsova in the fifth game of the second and third sets.
"I thought I did a good job in the first set, I had a little less match experience than her at the end but I stayed together, stayed tough and came through," Sharapova said.
Sharapova reached the semifinal for the fourth consecutive time since winning the WTA's season-ending championship in her debut in 2004.
"I'm really happy I didn't just stay home and quit and not come out here," said Sharapova, who has a lingering right-shoulder injury.
Sharapova's win also meant first-time qualifier Ana Ivanovic advanced to the semifinal out of the red group in the round-robin event.
-- Associated Press