In response, tennis introduced a new anti-corruption code in 2009 but were told previous corruption offences could not be pursued.
In subsequent years, there were repeated alerts sent to the TIU about a third of these players. None of them was disciplined by the TIU.
However, with the sports betting industry exploding in recent years, multiple sources told Reuters that the revelation was no surprise to those who closely follow the sport. Out of the spotlight at small tournaments around the world, the temptations are obvious and malfeasance very difficult to prove, sources added.
Betting on tennis is relatively simple and comes with enormous potential payoffs, a professional tennis gambler told Reuters under the condition of anonymity.
Trailing only soccer, tennis is the second most active betting market, shows research by the European Gaming and Betting Association.
The European Sports Security Association, which monitors betting for leading bookmakers, flagged up more than 50 suspicious matches to the TIU in 2015. The organisation also declared that tennis attracts more suspicious gambling activity than other sport.
All of the players under suspicion of match-fixing have been allowed to continue competing.
At the end of the first day of the 2016 Australian Grand Slam, several of the world's top players were asked to react to the allegations of match fixing.
Defending champion Novak Djokovich spoke about an incident in 2006 when it was alleged he had been offered $200,000 to throw a first-round match in St Petersburg, a tournament he did not eventually attend.
"I was not approached directly," he told reporters, The Guardian said. "Well … I was approached through people that were working with me at that time, that were with my team. Of course, we threw it away right away. It didn't even get to me, the guy that was trying to talk to me, he didn't even get to me directly. There was nothing out of it."
Several media reported that Roger Federer seemed particularly angry by the claim that one of the players under suspicion was a Grand Slam champion.
"I mean, it's, like, who, what? It's, like, thrown around. It's so easy to do that," he told reporters.
"I would like to hear the name. I would love to hear names. Then at least it's concrete stuff and you can actually debate about it. Was it the player? Was it the support team? Who was it? Was it before? Was it a doubles player, a singles player? Which slam? It's so all over the place. It's nonsense to answer something that is pure speculation."
Meanwhile, Maria Sharapova told a press conference said she hoped players would not be tempted to fix matches, whatever their ranking or income. "To me the sport has always meant a lot more than money. I know that the more successful you are and the more matches you win, the more prize money you will receive. But, ultimately, that's never been my personal driving factor in the sport. There's just so much more on the line."
Serena Williams said the first she had heard of it was as a warning that she may be asked about it after her win against Italian Camila Giorgi, "But that's literally all I have heard about it."
You can read the full report here.
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