The Welsh backs aren’t exactly sleeping like babies as they figure out how they will cope with new father Sonny Bill Williams.

Williams is poised to be restored at inside centre for the All Blacks in Saturday’s Test at Cardiff, four days after his first child was born on the other side of the world.

It has prompted some extra planning from Wales’ defensive coaching staff, charged with reducing the impact of the athletic code-hopper.

Welsh wing George North says quelling Williams’ power and ability to offload is high on the priority list.

“He’s a difficult guy to play against, he’s exceptionally strong in contact and has amazing hands,” North told AAP.

“The single arm flick has been a pain for everyone and you have to be well aware of his running lines because he’s very strong at carrying from his rugby league days.”

Williams and likely left wing Julian Savea will give the All Blacks backline a typically imposing appearance, but they are eclipsed by the monstrous Welsh, who boast arguably the world’s biggest back division.

Experienced centre Jamie Roberts is listed at 1.93m tall and weighs 110kg, shading Williams by 2cm and 2kg.

Savea is fractionally heavier than opposite Alex Cuthbert but is 7cm shorter than the towering Welsh right winger, who has scored in each of his last four Tests.

North, who also crossed in last week’s 17-13 win over Fiji, weighs 109kg, giving him a considerable size advantage over whoever he marks.

A consistent standout for Wales since his Test debut as an 18-year-old four years ago, North is looking forward to matching skill as well as muscle with the visiting backs.

“The southern hemisphere teams are very good at winning the aerial battle.

“They kick a lot and you are aware of what’s coming so you work even harder. There is no bigger challenge than the All Blacks.”