Defeat at Otago Stadium on Sunday would see the Irish return home without reaching the knockout stages, a heartbreaking conclusion to a campaign that has promised so much.
Just two weeks ago they routed Australia 15-6 in a result that stunned the World Cup and separated the Six Nations and Tri-Nations teams into opposite sides of the quarter-final draw.
Toppling the Wallabies may have issued a reminder that Ireland capable of beating anyone, but O'Driscoll insists Italy were always the gatekeepers to the last eight.
"It's win or bust. We always felt as though it would be a very important fixture," he said.
"We felt as though we had the ability to beat Australia, but winning that game hasn't made this group any different. We still have to beat Italy on the final day.
"We realise the magnitude of the match and look forward to that element of pressure.
"We're more relaxed in our own skin knowing that we're capable of that performance against Australia.
"It's about trying to improve on that. We'll be in a good place if we manage that."
Ireland have amassed a 15-match winning streak against Italy yet their hair-raising 13-11 triumph in Rome in February demonstrated that victory must not be taken for granted.
"They've become harder and harder to play in each match over the last four or five years," said O'Driscoll.
"Some of the scorelines have been getting closer and closer and we really had to pull it of the bag to beat them earlier this year.
"We respect the quality they possess and know that on their day they are a very good side."
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