LONDON • Daniel Koellerer - once regarded as the most unpopular player on the ATP World Tour - has emerged as one of the main sources of the controversial match-fixing allegations sweeping tennis.

As the leaders of the tennis world take stock of the serious accusations directed at the sport by BuzzFeed and the BBC, they are keeping track of some of the people who offered information to help compile the report.

The infamous name at the top of the list is Koellerer.

Now aged 32, the Austrian was banned from tennis for life due to charges of match-fixing which were investigated and prosecuted by the Tennis Integrity Unit in 2011. His ban was later upheld after an appeal to the Court of Arbitration for Sport.

Nicknamed "Crazy Dani", he once called a Brazilian opponent a "monkey" and told him to return to the jungle. He also spat in his hand before offering another opponent a handshake, causing a locker-room fight, and provoked his countryman Stefan Koubek so much on court that he was grabbed by the throat.

"All the players hate him," insisted Koubek.

Before his life ban, Koellerer's persistent bad behaviour on court resulted in him being suspended for six months by the ATP World Tour.

Yet BuzzFeed News and the BBC sought him out to help compile their "Fixing Files".

Koellerer told BuzzFeed that match-fixing was a widespread problem and claimed he knew of other players who were implicated.

"They were losing matches on purpose," maintained the Austrian. "Sometimes they were talking in the next locker. There were so many guys and of course, it's, like, big money in the game. For one stupid match, just losing."

THE TIMES, LONDON