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Frank Augstein, Associated Press
Australia's Scott Fardy during the Rugby World Cup Pool A match between Australia and Wales at Twickenham Stadium, London, Saturday, Oct. 10, 2015.

LONDON — With 40 matches down, three weekends to go, the Rugby World Cup has become a knockout contest between the hemispheres — North vs. South.

The defending champion, New Zealand's All Blacks, are playing France in the highest-profile of this weekend's quarterfinals, which also feature Australia against Scotland, South Africa vs. Wales and Argentina against Ireland.

Yes, six weeks is a long tournament. But when big men are colliding at full pace for 80 minutes without the benefit of helmets and much padding, it takes time to heal.

Two of the quarterfinal matches are at Twickenham, known as English rugby HQ, and two are at Millennium Stadium further to the west in Cardiff, Wales. The Welsh won't get to play in their capital, because England is the tournament host. England won't get to play at all.

It's the first time a tournament host has failed to reach the Rugby World Cup quarterfinals. They're joining the likes of so-called Tier Two countries Japan, which provided a brilliant cameo with three wins including an historic victory against South Africa, and the Pacific countries of Fiji, Samoa and Tonga on the sidelines.

England may have invented it, but New Zealand has taken on rugby as a national sport — elevating it to something akin to religion. They're taking their brand back to the world, and so half the teams still alive in the tournament have Kiwi coaches, including Steve Hansen's All Blacks. Warren Gatland at Wales, Joe Schmidt at Ireland and Vern Cotter at Scotland were all schooled the New Zealand way.

Here's some things to know ahead of the quarterfinals:

SOUTH AFRICA vs. WALES (Twickenham, London. Referee: Wayne Barnes, England. Kickoff: 1500 GMT/11 a.m. EST Saturday)

The Springboks have the best strike rate at the World Cup, having won the title twice since rejoining international competition in the post-apartheid era. Nelson Mandela presenting the winning trophy to the Springboks in 1995 when they beat New Zealand is still one of the most enduring moments ever at the tournament. South Africa won again in 2007.

The South Africans have only lost twice in 30 tests against Wales. And although they tend to do most of their work in or close to the rucks and mauls — the contests after a player is tackled when the ball is either raked with the feet or held in hand and becomes more-or-less a wrestle — the Springboks have two of the best try scorers in the business on each wing. Bryan Habana has equaled the great Jonah Lomu's mark of 15 World Cup tries and could earn the record outright with another touchdown against Wales.

On the plus side for the Welsh, they beat South Africa in Cardiff last November, and came through the toughest group of the tournament. Also giving the Welsh some hope — Japan had never beaten South Africa before, until the almost unthinkable happened on Sept. 18.

NEW ZEALAND vs. FRANCE (Millennium Stadium, Cardiff. Referee: Nigel Owens, Wales. Kickoff: 1900 GMT/3 p.m. EST Saturday)

While the All Blacks are the undisputed No. 1 team — with their intimidation tactics starting before kickoff with the ceremonial Haka — they've struggled to exert serious supremacy in important recent World Cup matches against the French, who thrive on their reputation for being unpredictable.

New Zealand beat France in the first Rugby World Cup finals in 1987 and in the most recent in 2011 — both played in New Zealand — but lost to inspired French comebacks in the 1999 semifinals and the quarterfinal in 2007, which was also played in Cardiff.

France lost badly to Ireland last weekend. That probably makes them more dangerous and New Zealanders more nervous.

"They love playing the All Blacks in big matches and I know they will perform out their skin," New Zealand fly half Dan Carter said. "That's one of their strengths. They can just flick a switch and turn it on."

Carter and captain Richie McCaw were part of the All Blacks team that lost to the French in '07. McCaw avenged that when he lifted the trophy after an 8-7 win in Auckland in 2011, but Carter missed that match with an injury. The leading scorer in international rugby has never played in a World Cup final, something he's determined to change.

Coming into the tournament, the All Blacks had only lost two tests in three seasons.

IRELAND vs. ARGENTINA (Millennium Stadium. Referee: Jerome Garces, France. Kickoff: 1200 GMT/8 a.m. EST Sunday)

Six Nations champion Ireland has won 12 and drawn one of their 20 matches against Argentina, and are on a five-match streak since losing all three head-to-heads in 2007. But Argentina has a 2-1 edge in World Cup encounters.

The Irish have never won a World Cup quarterfinal and they'll be without captain Paul O'Connell, who injured his hamstring against France, and flanker Sean O'Brien, who is serving a suspension.

Ireland pioneered the choke defense, when tacklers trap the attacking player and ball and hold them off the ground to stop the opposition recycling possession. It could be a factor against the Pumas, who are showing more attacking flair than ever and have only struggled in one game in the tournament — a loss to the All Blacks.

AUSTRALIA vs. SCOTLAND (Twickenham. Referee: Craig Joubert, South Africa. Kickoff: 1500 GMT/11 a.m. EST Sunday)

The Wallabies are strong favorites after topping a group containing Wales and England, and facing a Scotland team that lost every match in the Six Nations tournament, and struggled to hold off Samoa 36-33 to seal second spot in its group here.

But the two-time champion Australians are wary after losing two of their last three matches against the Scots. Scotland produced a 9-6 upset in Newcastle, north of Sydney, in June 2012 in conditions that Wallabies captain Stephen Moore recalls as the worst he's ever played in — torrential rain and a howling wind. The forecast isn't that bad for London.