After one day of the World Cup, 11 cards have already been shown, and there were signs that referees are prepared to clamp down hard on misdemeanours.

The last World Cup saw a record-breaking 345 yellow cards and 28 red cards issued, and after two games of the 2010 edition we are already up and running with the first sending off of the tournament.

Here are some of the more significant decisions of the opening day's play, and what they tell us about how the rest of the tournament will unfold:

Gerardo Torrado (Mexico) on Reneilwe Letsholonyane (South Africa)

Decision: Free-kick

A nothing free-kick for a simple aerial challenge, the penalisation of Torrado shows that referees are not prepared to tolerate any higgledy-piggledy in the air. Any sign of a raised arm, or using an opponent to gain height, and the referee will blow up. Fabio Capello should take note if he intends to use Peter Crouch at any stage.

Pettiness rating: 4/5

Steven Pienaar (South Africa) on Rafael Marquez (Mexico)

Decision: Advantage

A fairly venomous challenge from behind, referee Ravshan Irmatov could easily have stopped play, and in previous World Cups, would have had no hesitation in doing so. But he rightly spotted that Mexico had the ball in a threatening area and played the advantage. Clearly Fifa have encouraged referees to seek to keep play going if possible, which can only be a good thing.

Pettiness rating: 2/5

Kagisho Dikcagoi (South Africa) on Giovani dos Santos (Mexico)

Decision: Free-kick, yellow card

South Africa's first yellow card of the tournament was not given for a dirty challenge or a reckless lunge, but a simple hand on the arm. This was a theme that developed through the day's games: referees are looking out for any sign that players are being impeded. That used to mean shirt-tugging, but even offences that would once have been given simply as obstruction, are now deemed worthy of the notebook.

Pettiness rating: 3/5

Nicolas Lodeiro (Uruguay) on Bacary Sagna (France)

Decision: Free-kick, second yellow card

Yuichi Nishimura had no choice but to make Nicolas Lodeiro the first sending-off of South Africa 2010 after flying dangerously at Sagna. The message was clear - it may only be day one, and you might only have been on the pitch for 20 minutes, but a sending-off offence is a sending-off offence. Remember that when the latter stages come along.

Pettiness rating: 2/5

Diego Lugano (Uruguay)

Decision: Yellow card

The Uruguay captain found that the referees at this World Cup have a very low threshold for delaying tactics. He was booked for prevaricating while Thierry Henry lined up to take a late free-kick. At every tournament it falls to a certain player to see exactly how far the patience of the referees can be tested. Lugano found out, and every other player at this tournament owes him a debt of gratitude as a result.

Pettiness rating: 4/5