Mo'unga thought he did a 'good job' at halfback until de Groot's feedback

With No 9 Aaron Smith yellow carded for a deliberate knock-on, the All Blacks decided to move first five-eighth Richie Mo'unga into halfback during their quarter-final clash with Ireland.

New Zealand spent the vast majority of their 10 minutes without Smith on defence, opting for a high volume of kicks to see them through the spell while down a man.

One try to their opponent's halfback Jamison Gibson-Park closed the lead to one just before halftime, but stoic defence saw the Kiwis survive all further efforts from the Irish as Smith re-entered the fixture six minutes after the break.

Mo'unga's passing is of course world-class as the All Blacks' preferred playmaker and the 29-year-old even put up a box kick, steering the team relatively seamlessly through the spell in his few touches behind the ruck.

Where his skillset couldn't save him though was at scrum time.

Having survived a cross-field kick just inches from their own try line, the All Blacks received a scrum on the five-metre line and Mo'unga was tasked with the scrum feed.

"At halftime, I had to ask Nuggy (Aaron Smith), I was like 'how do I put the ball into the scrum?' I asked him that," Mo'unga told the Front Row Daily Show.

"He showed me, he was like 'wait for Codie (Taylor's) foot to come out and aim for his bottom sprig and he'll just kick it back.'

"I've never squatted so low, in the scrum, I got real low and I was waiting, Codie's foot took ages. I thought I did a good job and I came back and Grooter (Ethan de Groot) was like 'you could have left it longer!' I was like bro, I didn't even know that was a possibility."

It's hard to imagine a worse time to feed your first scrum, five meters from your own try line in a quarter-final against the world's number one ranked team leading by just one point, but in winning the scrum and making a clean exit, the All Blacks again proved their composure under pressure.

It was Mo'unga who had just denied an Irish try by challenging Peter O'Mahony in the air for Gibson-Parks' kick, giving up significant height in the contest.

"I said it earlier in the week, we're playing Ireland, the best team in the world but we wanted to be the best team today," Mo'unga added.

Smith's yellow wasn't the only card the All Blacks received, Codie Taylor was sent off in the 63rd minute for collapsing a driving maul which consequently resulted in a penalty try.

The All Blacks had to replace the hooker in that instance and Dane Coles took the field. Second five-eight Jordie Barrett commended the effort in the sheds after the match.

"It's unbelievable," he said. "A couple of yellow cards, plenty of what ifs and we defended three or four minutes in one phase play at the end there and Sammy Whitelock came up with the plum. So, unbelievably proud.

"We had a lot of trust in our defensive system in the end, we've been building that for a little while so it's super special."