New Zealand attack coach Joe Schmidt is using his famous attention to detail to try to plot the downfall of his former charges ahead of the All Blacks' Rugby World Cup quarter-final against Ireland on Saturday.

Four years ago, Schmidt was the Ireland head coach when his team was steamrollered by a purring All Blacks at the same stage of the 2019 World Cup in Japan.

He left the role after the tournament having enjoyed six successful years at the helm, and last year he returned to his homeland to join All Blacks head coach Ian Foster's staff.

With his former assistant Andy Farrell now head coach of the world number one ranked Irish, the build up to this match has been dominated by speculation over what impact Schmidt will have on proceedings, and how his insider knowledge could tip the scales in New Zealand's favour.

But the All Blacks were quick to play down that aspect following their training session on Tuesday.

"Joe's been just driving our game and what we can do better," said forwards coach Jason Ryan.

"He's really challenged the group, as we all have as coaches, (on) how the All Blacks can be better."

For the players, the man dubbed a coaching genius during a nine-year stint at Leinster and then Ireland, has brought meticulous planning to the practice field.

"Joe just sees the game in a very detailed view," said centre Rieko Ioane.

"Especially with us backs, his work in noticing trends in other teams' attack and defence is what separates him, and just the detail he goes into.

"For us, trying to find those one percents can be quite hard, but with Joe he makes the view of the game a lot easier by the way he understands it.

"He's definitely helped us quite a bit."

- 'Be careful what you ask' -

Schmidt's Ireland stint hit glorious heights in 2018 with a Six Nations Grand Slam, a first ever home win over New Zealand and a series win away to Australia.

But the wheels fell off the very next year and his tenure ended in ignominious fashion as Ireland were dumped out of the World Cup by New Zealand in a seven-try 46-14 thrashing.

One criticism levelled at Schmidt was that his coaching methods, once lauded for transforming Ireland, were now questioned for being joyless.

And veteran All Blacks scrum-half Aaron Smith alluded to as much when explaining what Schmidt had brought to the camp.

"He always has clips to show you if you ask, so you've got to be careful what you ask because it could cost you 20 minutes," quipped Smith, who scored the first two tries in that Tokyo romp four years ago.

"But the last 18 months, I've really enjoyed connecting with him.

"He sees the positives in your own skillsets, so doubles down on that, and a lot of the stuff is around just effort."

bc/pi