Crystal ball time. Greg Growden puts on his tatty old Wizard suit and predicts what will and won't happen during the World Cup quarter finals.

South Africa v Wales

The crucial factors: Can the old Springboks legs hold up, and do Wales have enough sturdy legs left?

The South African team has looked appreciably better after Jean de Villiers was forced from the tournament through injury, enabling the Springboks to play a more penetrative midfield, and when coach Heyneke Meyer at last realised that instead of veteran Victor Matfield he had to play the younger lock combination pairing of Eben Etzebeth and Lood de Jager.

There is still a lot of experience left in this South African lineup, which will give them the edge over Wales, who have been shackled by endless injuries.

Filo Paulo© Stu Forster/Getty Images

If Wales had been at full strength, they would have come close to winning the Webb Ellis trophy, but as shown against Australia the previous week, the attrition rate is starting to wear them down. If they had their best Wales backline playing, it was highly likely they would have seized upon their two man advantage during the second half.

Instead those left got caught up in white-line fever, wasting the moment to properly stretch the Australian defence by too often cutting back into the middle of the field rather than pushing possession towards the outer fringes. Opportunity lost.

Man of the match: Fourie du Preez (South Africa). We are talking about a proper man of the match, not the stupid system used in the World Cup when it is decided by social media, prompting the embarrassing situation of England's Joe Launchbury receiving the award after his team had been belted by Australia. Du Preez is class, and should control this game when the pressure builds.

The impact of the referee: The most dangerous person for teams at this World Cup have been the citing commissioners, who several days after games have often disrupted preparations by forcing hearings and with it inevitable suspensions. The refereeing at the tournament has so far been reasonably good, and Wayne Barnes has avoided upsetting too many people. Both teams are reasonably familiar with him, and know how to adapt to him, which should temper his impact.

Liam Williams© Steve Bardens - World Rugby/World Rugby via Getty Images

Potential of an upset: A reasonable possibility. South Africa are favourites, but Wales are the physical type of team who can frustrate them because they are so competitive at the breakdown. You can never underestimate the Welsh spirit, and like Eddie Jones with Japan, Warren Gatland is street-wise to know of a few ways to disrupt the Dad's Army outfit in the tournament. His choke tackle approach against the Wallabies to force scrum feeds from held up mauls almost worked, except Wales had no counter for the Australian sweeping defence.

Tip: South Africa by 3

New Zealand v France

The crucial factors: It's all in the mind.

New Zealand always go a bit wonky when they confront France at World Cup finals time, because it brings back so many horrible memories. However if they just keep their heads, they should easily account for France, who were so underwhelming in their last game against Ireland.

© Stu Forster/Getty Images

While New Zealand have been way off their best during this tournament, they know how to peak. As long as their set piece remains solid, and they subdue the France backrow, a comfortable win appears inevitable. Expect Daniel Carter to quickly take control, reverting to a game which he has used often with success against Australia, mixing it up with decisive chip kicks just in behind the France defence, to constantly turn them around, as well as testing the French back three with high kicks to the corners. There are glaring weaknesses out wide with France, and Carter knows how to expose that.

Man of the match: Kieran Read (New Zealand). He is a real big game player, and will be crucial in nullifying the impact of France's strongest asset- its backrow. Read has been a little off-key this tournament, but that is bound to change.

New Zealand's Kieran Read© Shaun Botterill/Getty Images

The impact of the referee: The All Blacks would be delighted that they haven't got Barnes, as they like blaming him for everything, but they also know it is difficult to get on the good side of Nigel Owens. Owens doesn't stand for too much nonsense, and so expect a number of penalties going either way at the breakdown. Owens loves to assert his authority. Penalty goal kicking will be crucial, and here New Zealand has a good advantage. Carter is generally reliable in the big encounters, and you can expect to hear Owens' whistle often.

Potential of an upset: Zilch. France doesn't have the attack to properly threaten the All Blacks.

Tip: New Zealand by 20

Ireland v Argentina

The crucial factors: It revolves around attrition.

Can Ireland overcome the loss of so many big name players, none more crucial than their openside flanker Sean O'Brien- one of many to be tripped up by World Cup citing commissioners?

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O'Brien is exactly what is required when confronting the Pumas, as he has the ability, as he did against France, in completely dominating the tackle area during this quarter-final. Paul O'Connell and Peter O'Mahony are other serious Ireland losses. You should never under-estimate the Irish spirit- as they are as potent as the wounded Welsh- but Argentina through the experience of playing in several Rugby Championships- should know how to nullify that- especially as their play is these days far more balanced, and no longer focused entirely on bashing up their opponents via the scrum.

Man of the match: Nicolas Sanchez (Argentina).

Competent No. 10s are crucial at World Cup finals time, and the Pumas have a good one in Sanchez, who knows how to mix up the Argentinean game. Hopefully the Pumas don't go for their usual up-front dominating game, but also give their attack a chance, because it is better than a lot of people assume.

Juan Martin Hernandez goes past Giorgi Nemsadze© Laurence Griffiths/Getty Images

The impact of the referee: Teams often get a bit edgy when they confront French referees as like their national team they can so unpredictable. Jerome Garces is relatively consistent, and knowing that this will be a highly physical encounter is certain to try to take control early on. That could affect the flow of the game, which may help Argentina; especially as their goal kicker Sanchez is reliable. How Garces polices the set piece will be important, as while the Pumas are good up front, their lineout is open to scrutiny.

Potential of an upset: Very high. Ireland are favoured by the bookies, but the loss of key players will hit them hard.

Tip: Argentina by 4

Australia v Scotland

The crucial factors: Can Australia forget history and show they are at last consistent, and can Scotland overcome, like Ireland, serious losses via the citing commissioner?

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Scotland, who has as their director of rugby a person in Scott Johnson who knows Australian Rugby backwards, have a way of upsetting the Wallabies, inflicting several recent embarrassing defeats. Scotland will be using that fact as an important motivational tool, as shown by Sean Lamont remarking: "You can take us for granted all you want and you'll get bit on the arse."

Even though the often arse-bitten Australians are the masters of losing the supposed easy ones, their hopes have risen after two Scottish forwards Jonny Gray and Ross Ford were cited and suspended for the rest of the tournament. To have any hope Scotland needed absolutely everyone available.

A weakened Scottish forward contingent will still try to be as destructive at the breakdown as Wales were last weekend, which affected Australia's attacking flow. But the Wallabies are now more mindful of not getting caught high at maul time.

Man of the match: Michael Hooper (Australia).

He's rested after missing the Wales pool match due to a citing and primed for a big one. Expect crucial Australian turnovers, and more opportunities to properly attack than in the Wales pool match. Hooper is bound to be sighted often in open play, causing havoc.

The impact of the referee: Australia will be in two minds about Craig Joubert. While they have a good relationship with Joubert, and in the back of his mind now knows their scrum is pretty good, he did send two Wallabies to the sinbin last weekend, which would have led to their defeat if the Australian defence did not hold up so stoically.

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So Australia will be trying to stay on their best behaviour to avoid it happening again, while Scotland will be doing all they can to antagonise them in the hope of enjoying the advantage of lopsided player numbers. Yes, Joubert will have an impact.

Potential of an upset: Highly unlikely. While some are saying Scotland should not be underestimated, their defence, exposed by Samoa, is nowhere near good enough for major matches while their game plan sometimes lacks a real focus. Hope only takes you so far and Australia are in another class.

Tip: Australia by 18