Kewell said he is not on speaking terms with Viduka.
Viduka accused Kewell's agent, Bernie Mandic, of trying to persuade Aussie coach Frank Farina to make the Liverpool star the SocceRoos' captain, something which still upsets him.
"Until he actually apologises for saying those things I'm not going to go out of my way to be nice to him," said Kewell.
"Ultimately he said some nasty things that were so vulgar they couldn't even be printed.
"Fair enough, if he had said it to my face but to slag me off behind my back and then deny it when it's all on tape is pathetic. I ain't going to be friends with him."
And on O'Leary, Kewell said in the football magazine, FourFourTwo: "I wasn't disappointed to see him get the sack. He took us as far as he could and we needed some fresh blood.
"When he first took over he was a good man but then something happened. I don't know whether it was him, the club or the players.
"My relationship with David O'Leary was iffy to say the least. I did enjoy working with him but that faded away because things happened.
"I had conversations with him that left me bamboozled. He was saying things that I didn't understand. I was left gobsmacked half the time.
"I would just shake my head and think, 'What?' He was my boss and I couldn't argue with him but I used to just sit there (in disbelief)."