Di Canio took over from O'Neill and kept Sunderland up at the end of last season.
When asked about the end of his stint on Wearside, O'Neill said: "Paolo di Canio? That managerial charlatan? Paolo stepped in there and basically and, as weeks ran on, he ran out of excuses. I had a wry smile to myself.
"It's like a 27-year-old manager stepping in and the first thing you do is criticise the fitness of the team beforehand. If you've ever seen Aston Villa play, you'll see the one thing I pride myself on is teams being fit.
"What you'll find interesting is that when he started, the team wasn't fit for the Chelsea game. Then the following week when he won at Newcastle, not being fit wasn't mentioned. Then about two weeks later they got mauled by Aston Villa, someone asked him about the fitness.
"Suddenly, he didn't know where to go. Because the team, as it progresses, should be getting more fit. And then, at the start of the season, when he lost by a late goal at Southampton, he was asked about the fitness regime, that he was going to have them the fittest team in the league. Suddenly, the fitness wasn't for that game but for Christmas, when the winter months set it. You know I did have a wry smile at that one."
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