The Saracens stand-off had been struggling with injury, having playing just once this month and being put under pressure for his starting place by Bath's George Ford and Northampton Saints' Stephen Myler.
However, Lancaster revealed that the number 10 shirt will be Farrell's if he comes through the match against the Irish province unscathed.
He is quoted by The Mirror as saying: "I trust Owen, he'll be ready. We've never been afraid to put players in for the first game but you have to get the balance right when you're playing the All Blacks.
"Cohesion and experience is important to us and of the fly-halves we have, Owen is our most experienced.
"He has to do well this weekend because he has some competition. But he's a good player and has been a good player for us. That has to count for something."