Winning your pool in the Rugby World Cup doesn't guarantee an automatica path to the semi-finals. In the history of the World Cup, only seven of 12 pool winners have successfully negotiated their path past pool runners-up to get to the semi-finals. Of course, the current format was only introduced in 2003 after the quarter-final playoffs in 1999 - where Ireland infamously lost to Argentina in Lens.
In fact, if you only look at the last two tournaments, only three pool winners of eight have made it to the semi-finals.
Upsets will happen - we've already seen that this World Cup. But which pool winner is most likely to continue the trend? Here is our ranking of the most likeliest upsets on this World Cup quarter-final weekend.
1. Ireland v Argentina
At the time of writing, despite the loss of Paul O'Connell, Johnny Sexton, Peter O'Mahony, Sean O'Brien, and Jared Payne - Ireland are three points favourites. In what was very close to a pick 'em game before Sexton was ruled out, it seems very odd to me that Ireland are still favourites.
That doesn't mean that I don't think Ireland can or will win, but they should be the underdogs for me. Argentina have played themselves into some great form - pushing New Zealand close just a few months after beating South Africa. They have young studs like Santiago Cordero, Pablo Matera and Fernando Isa to compliment the likes of Juan Martin Fernandez Lobbe, Agustin Creevy, and Juan Martin Hernandez.
The Argentines have close to the strongest scrum in the tournament, their maul is outstanding and they have playmakers in Nicholas Sanchez and Hernandez who can make the most of the snappy and snippy service from Landajo at scrumhalf to release Joaquin Tuculet or Cordero.
I think Argentina will score more tries than Ireland, and a lot will come down to Joe Schmidt's smarts and Ian Madigan's boot.
2. South Africa v Wales
In an alternate universe where the Welsh rugby team hadn't broken themselves against England, I'd fancy them as strong favourites to beat South Africa. The Boks are a team in transition. The older players are a year past it, and the young players need another year experience.
Japan and Argentina have beaten the South Africans this year, and there is no reason why Wales can't.
You'd be nervous backing Wales with a 20-year-p;d in the centres against Damien de Allende and Jesse Kriel.
3. New Zealand v France
France are not a good team. If Ireland were really worried about losing O'Connell and Sexton, then they shouldn't have beaten France. They have one gameplan - "POWER" (Jeremy Clarkson approves). New Zealand are too good for that. They will not succumb to the pressures of 2007, and I fancy New Zealand to rip through France by several scores - just like Ireland should have done.
The over/under points total is 40.5. New Zealand should get that alone.
4. Australia v Scotland
If there is one coach in World Rugby that can rival Joe Schmidt's smarts - it's Michael Cheika. With a lot of talent to use with Australia, Cheika has developed his style and can exploit any opposition weakness. His use of Pocock and Hooper against England was so effective, and they will be more than a handful for the winners of Ireland and Argentina.
They have rested Folau and Pocock, which tells you everything you need to know about how strong Scotland are. Don't get me wrong, Scotland are an improving side. Vern Cotter has them playing some great rugby, and they will continue to develop - especially with the likes of Josh Strauss, John Hardie, Mark Bennett, and Stuart Hogg in their ranks. Scotland will finish no worse than fourth in next year's Six Nations, and I think they will win the Six Nations in the next five years.