The first 16 games in Qatar saw referees reach into their pockets to issue 52 yellow cards and a single red.
Aside from the prospect of a second yellow leading to an automatic sending off, the bookings also have an impact on team selection in future World Cup games.
Coaches may be tempted to bench those already on a yellow card, due to the system of suspensions adopted by FIFA to punish players and teams who do not follow the rules of the game.
Here’s everything you need to know about the system, and the players who are already missing games.
What happens when a player receives a red card?
Any player who is shown a straight red card during a game will automatically be handed a one match ban in the tournament.
FIFA also reserve the right to investigate the nature of the red card and impose additional sanctions if they feel they are required.
What are the rules for yellow card bookings?
Unlike in the Scottish domestic leagues, where a player needs to receive five yellow cards before they are punished with a one game suspension, at the World Cup players miss a game after just two bookings in different games.
When are the bookings reset?
There is some good news for players who have received a single yellow card though – all bookings are reset after the quarter finals stage.
This means that any player who is shown a second yellow card of the competition in the quarter final will not miss out on a place in the semi final.
It also means that any player who is shown a second yellow card of the competition in the semi final will still be able to play in the final (unless they are sent off in the semi final).
What players are currently suspended?
A few players have already picked up two yellow cards, or a single red, and they are as follows:
Wales goalkeeper Wayne Hennessey received the first red card of the World Cup in Wales’ second group game against Iran and will miss the final group game against England.
Iran’s Alireza Jahanbakhsh will miss Iran’s final group game against the USA after picking up his second yellow card in the Wales game.
Saudi Arabia’s Abdulelah Al-Malki is suspended for his team’s crucial game against Mexico, with Costa Rica’s Francisco Calvo missing the game against Germany.
A Belgium’s Amadou Onana’s two red cards count him out of playing Croatia.