The Uruguayan is now retired at the age of 39, but played for Cagliari from 1995-2000, going on to Juventus in 2000-02 and Perugia for six months.
"I fixed games myself in Italy," O’Neill told Montevideo.com.uy and calcionews24.
"Against Chievo Verona we (Chievo and his Cagliari side) would have been safe from relegation with a draw, and the clubs would pay us a $60,000 bonus each.
"I went to speak to their captain and we all placed bets on a draw.
"In the 87th minute one of our players scored and we went 2-1 up, a shot from 40 metres that went into the top corner. That wasn't supposed to happen!
"So I shouted at Diego Lopez: 'Concede a goal or they’re going to kill us.' Diego lost possession and they scored the 2-2 final result.
"It wasn't the only time, as I did it with Perugia too, as I was captain and we all placed bets."
The 2-2 draw with Chievo was on June 14 1998 and his then team-mate Diego Lopez is currently co-coach of Cagliari.
O'Neill was always a controversial character and also confessed to repeatedly punching Gattuso during a match against Milan.
"Gattuso had a reputation for provoking the South American players, so I promised I'd punch him.
"During a close tussle I smacked him and hoped I'd receive one back. He looked like he wanted to kill me. We continued with threats - all in Italian - and I punched him again."
O'Neill, who is of Irish descent, also admitted having a drinking problem while he played.
But he added that, while his team-mates were not so fond of the booze, at least he kept his hands to himself as far as women were concerned.
"I drank a lot back then and had a few problems with tests. Nothing happened at Cagliari because the president adored me.
"It was different at Juventus, as every month they did blood tests and I had high cholesterol among other things. The doctor used to say I should have been locked up rather than playing football.
"Once at Juve I went to a party at Pippo Inzaghi’s house and there were lots of girls from TV shows there.
"We danced and drank beer, but everyone except me ended up having sex that night. The day after I saw them on television and told my wife: 'Look, last night I was with all of them and didn’t do anything!'"
- Sports & Recreation
- Gennaro Gattuso