http://www.bbc.com/sport/0/football/28221119

The most popular system has been 4-2-3-1, the same as it was in South Africa four years ago, but what has changed is how flexible the players have to be in that formation.

When they have possession, some of those teams playing four at the back send their full-backs forward as if they were wing-backs.

They split their two centre-backs and have a midfield player dropping back between them to give them a three-man defence.