Tadhg Furlong has warned that to switch off even for a second against New Zealand will cost Ireland the chance of a maiden Rugby World Cup semi-final.
Ireland will face back-to-back world champions New Zealand in the quarter-finals, after hosts Japan dumped Scotland out of the tournament with a stunning 28-21 victory in Yokohama.
Japan's fine triumph sent the hosts top of Pool A and booked the Brave Blossoms a last-eight clash with South Africa.
That left Ireland second in the pool to set up a last-eight meeting with the All Blacks on Saturday in Tokyo, with prop Furlong in no doubts about the size of the task ahead.
Asked for the key to beating the All Blacks, Furlong replied: "Hard work, really. They are so dangerous.
"You can't switch off, at all. So it's just working really hard and staying switched on mentally because they can make something out of nothing with some of the players they have.
"I suppose there's an element of just being physical.
"It's the same any rugby game you play but as a front-five forward, it's all about being as physical as you can and hopefully coming out on top."
Ireland toppled the All Blacks for the first time in history in a stunning 40-29 win in Chicago in 2016.
Then head coach Joe Schmidt's men saw off New Zealand for their maiden win in Dublin in November's fine 16-9 victory.
That left Ireland team of the year, Schmidt coach of the year and Johnny Sexton player of the year in a clean sweep at World Rugby's 2018 awards.
While 2019's third-place Six Nations finish and a record loss to England in August left Ireland frustrated ahead of jetting into Japan, Schmidt's men will now eye reaching the World Cup semi-finals for the first time.
While Ireland will certainly be buoyed by those recent memories of beating New Zealand, British and Irish Lions prop Furlong warned his side not to enter the quarter-final with any preconceptions.
"I suppose you can draw a bit of confidence from previous wins but rugby evolves and it evolves quickly," said Furlong.
"We haven't played them that recently now really, and the game moves on, things changes, systems change.
"It gives us confidence that we have got results in the past but at the same time it doesn't guarantee you anything.
"It doesn't mean they're going to rock up and play the same plan as before."