His form earned the 23 year old a place in Giovanni Trapattoni's Republic of Ireland squad for the Euro 2012 finals in Poland and Ukraine.
O'Neill said: "It is a big season for him. There is obviously always talk about second season syndrome, that type of stuff, but I have a good belief that I don't think it will affect him.
"He has come back, he's done exceptionally well in training here. He looks every bit as strong as he was before and he looks every bit as determined.
"I don't think those sort of things will bother him."