There are a million cases of football players not reaching their full potential and O'Neill is certainly one such case. The attacking midfielder had all the tools in his locker but was unable to consolidate his place among the world's elite.
'The wizard', as he became known, shone during his time with Nacional in his homeland and quickly made the jump to Europe with Cagliari.
He arguably played his best football with the Italians, scoring 15 goals in 160 games and earning himself a move to Juventus in 2000.
That switch gave the Uruguayan the chance to line up alongside Zidane, who he impressed hugely, with the French star later admitting that O'Neill was the best player he had ever played with.
However, for all his talent, O'Neill wasn't one to work particularly hard and he was ushered out of the Juventus exit door just a year after joining due to his off-field conduct.
In the end his ascent to stardom proved every bit as rapid as his descent, with him hanging up his boots at the age of 30 and returning to his homeland.
After being convicted of match-fixing in 2012, O'Neill now spends his time living and operating his cattle ranch, having lost the millions he earned as a pro.
"I had $14m and I lost it all, I don't care about being poor," he told 'El Pais'.
A world away from that of professional football, Fabián lives a quiet life in his hometown of Paso de los Toros, something he is more than happy with. "I want to keep going like this, I don't want to be beside rich people. I never wanted that, I was rich. Thankfully there are still some ethics in the world. People who seen that I'm struggling and lend me a hand," he added.