Houllier decided to make public last month that he expects more from Ireland on the training pitch and during games.
But he said on Friday: "I am very patient and I hope everyone is as patient as I am. His attitude is fine. I expect more than he can give at the moment."
He added: "He knows. This is not an issue. I am prepared to talk about the team, not individuals.
"All I know is he has just come to the club. Whether he wanted to come to the club, I don't know.
"As a player, he has got something special. I like that. But his input has got to be better."
Ireland came to Villa at a value of around Â£8 million as part of the deal which saw James Milner head in the opposite direction to Manchester City in August.
He struggled to force his way into the side but was included in the starting XI for last weekend's 2-0 reversal at Blackburn.