O'Driscoll missed the Irish defeat in Paris, which preceded Wales' win over Scotland at the Millennium Stadium.
But despite the teams' contrasting fortunes last week, Hanson is still rating his side as underdogs.
The New Zealander, who will take over as the All Blacks assistant coach after this season's RBS 6 Nations championship, said: "Ireland are a better quality side than Scotland for a start.
"The sheer experience of the Ireland side makes them difficult.
"Like Scotland, Ireland have a good line-out so we will have to make improvements there and if Brian O'Driscoll comes back they are going to be pretty potent in the backs as well.
"They missed O'Driscoll in Paris and you are always going to miss someone who is world class. He is simply the best there is in his position.
"Ireland have gone through a great period and though they have lost three in a row recently, two of those were against France. So I don't think you can read too much into that.
"They will fancy themselves over us but we don't mind going in as underdogs."
Hansen claimed Wales will not get carried away despite their comprehensive victory over the Scots.
"The players have been pretty good. They realise that we have done just one small step and that there is still a long way to go.
"But at the same time you want them excited as well and it's better to have them like that than as at the same time last year."