The Irish boss said: 'Wales have their backs to the wall. They will view this as probably their only remaining opportunity to win a game because they have to travel to Paris for the last match.'
'Wales are at their most dangerous when they are given a bit of room to run. We need to be very clear about our game plan and carry it through by putting them under pressure and keeping them pinned down.'
Ireland announce team for Wales match
Ireland may be hot favourites to win the match, and maintain Wales' 100 per cent loss record in this year's tournament, but O'Sullivan says there will be no complacency in his side's preparations.
"There's no point in talking about England unless we close the deal in Cardiff. I've no doubt it won't be easy."
Williams sends out warning