What is it about the opening game of the World Cup that makes it more likely for an upset to happen than on the opening day of the Premier League season each summer?

In previous World Cups, Cameroon beat Argentina in 1990, Senegal beat France in 2002, Belgium defeating Argentina in 1982 and so on. But think back to opening days of the Premier League seasons when relative minnows played the Big Four and very few upsets come to mind.

There were close calls. Chelsea had to wait until late in the game for Hernan Crespo to score the winner against Wigan Athletic in 2005. Last season, Newcastle came close to beating Manchester United in their opening game at Old Trafford when the score ended 1-1.

As far as the last time a Big Four team lost on the opening day of the season, we have to go as far back as 2000 when Sunderland beat Arsenal 1-0 with a goal from now-Sunderland chairman Niall Quinn in a game where Patrick Viera was sent off.

So what is it about the Premier League where Big Four defeats on the opening weekend of the Premier League are so rare? And if there will be any upsets this weekend, which games will they be? Chelsea versus Hull? Everton against Arsenal? Manchester United vs Birmingham, or Spurs against Liverpool? Click the comments link below to share your opinion.