All Blacks centre Conrad Smith has been described as a 'master of outside centre play' by former Irish rival Gordon D'Arcy.

D'Arcy was writing about the qualities of centre play in The Irish Times and looking at the mistakes young Springbok centre Jesse Kriel made in his side's loss to Japan.

Kriel, 21, had been caught in the no-man's land that can affect a fullback or wing who has been moved to centre.

"A centre must develop spacial awareness to survive in Test rugby. If you get too close to an attacker, you end up following him into the space and it's almost impossible to get back out.

"It's about hovering two or three yards outside the tackle area so if he doesn't get the ball you push off to the next guy.

"If you dive into that hole and don't make a clean tackle you disappear from view and it looks like someone else has missed a tackle. Your team-mates know who is to blame. So does your coach," D'Arcy said.

Kriel's inexperience had been utilised by Japan especially when scoring their match-winning try.

D'Arcy said centre as an art form began with defence and that wasn't necessarily just tackling, but defence. The golden rule of defence in midfield was to stay relevant.

"Usually it's a prerequisite for a good defender to be a good tackler but the great one's might only make three or four primary hits in a game. It's about being in the right place at the right time," he said.

"[Former New Zealand player] Jared Payne instinctively gets this. Conrad Smith and Brian [O'Driscoll] are masters of outside centre play – it's their longevity and brilliance in defence that made them great players as much as the magic they conjured up passing out of contact or breaching defences.

"Smith's body shape in the defensive line is fantastic. His ability to move when crouched really, really low, laterally, forward or backwards means he rarely misses a tackle," D'Arcy said.

He added that he felt Payne had become the second most important player in Ireland's backline, and possibly the team.

"A fullback by nature, he has become a reliable Test centre and that's down to fundamental skills.

"He does the right thing at the right time," he said.

The toughest centres D'Arcy found to defend were Frenchman Mathieu Bastareaud and All Black Ma'a Nonu.

"Nonu was like tackling a rhinoceros," he said.

"There wasn't a game I played against Bastareaud when he didn't swat me aside…Bastareaud is actually a good defender. Many teams have targeted him but he holds the space so well that they end up running into him. And there is a lot of him," he said.