Veteran centre Conrad Smith talks about the "special rivalry" the All Blacks have with the Springboks.

One of rugby's greatest rivalries takes on added significance this week with the biggest match between the All Blacks and Springboks in 20 years.

Over that period these two nations have combined for some of the most enthralling contests, many of which could have gone either way. Often one moment of brilliance swings the result.

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Phil Walter/ Getty Images All Blacks midfielder Conrad Smith in training for the Rugby World Cup semifinals.

Israel Dagg's last-gasp try broke John Smit's heart in his 100th test in Soweto five years ago - the one where Ma'a Nonu gave the last pass wearing one boot. And the two epic battles at Ellis Park, where the results were split in 2014 and earlier this year, are others which immediately spring to mind.

None, though, carry the same magnitude as Sunday's World Cup semifinal, the first between these staunch foes.

Twickenham will weave another chapter in the rich history that includes the 1995 World Cup final; 2003 quarterfinal and third and fourth playoff in 1999.

Of those World Cup knockout games, the Boks hold a two-one advantage over the All Blacks, who claimed the quarterfinal in Melbourne 29-9.

From a New Zealand perspective, the Boks represent the pinnacle challenge. That sentiment is only enhanced by what's at stake this week.

"They're a special opponent. They hold a special place in our rivalry," veteran All Blacks centre Conrad Smith, who has played the Boks 17 times in his 92-test career for 13 wins and four losses, said.

"I grew up during the apartheid era so Australia were always the traditional foe. With South Africa coming back in it was something I didn't know as a child but was soon aware of how big the rivalry was. For me in my time, it's got back to where it was previously in terms of they are our ultimate rivals.

"Most guys would agree there's something special about playing them. Meeting them in a semi will be extra special."

A mutual respect has emerged between the two countries, borne of the ferocity of the collisions, and an understanding of the unique pressures and expectations placed on the respective teams.

"We have a good relationship with most teams we play but they have a respect for the game and for each other," Smith said.

"The game is treated a lot differently in our two countries. We are able to play each other at our peak and then walk off the field, shake hands and somehow in five minutes after a game we'll be chatting to them. That's something you enjoy, especially the more you play you savour those experiences."

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A sneaky - and somewhat controversial - lineout move saw Richie McCaw score a match-winning try in the dying stages of the All Blacks 27-20 win in Johannesburg this year, the last time these two sides met. But they were not entirely proud of their efforts that day and realise the size of the test before them.

Whatever happens, the rugby world are sure to be treated to another memorable occasion.

"There's something with South Africa with that consistent level of physicality and performance. We never seem to catch the other on off nights which sometimes happens with other teams and you get bigger margins.

"In the last five or six years it's been tight. It's comes down to two or three turnings points. They're always tight match-ups and I'm sure this one will be the same."