World Cup coaches are worried about yellow cards this week. Here’s what to know

For example, the United States had already clinched it's group before Thursday night's match with Turkey, but had four players already carrying yellow cards. That left coach Mauricio Pochettino with a decision whether to sit several of his star players.

To play or not to play?

At this stage, a referee's whistle and move to his pocket is the stuff of nightmares for fans, players and coaches. A player already given a yellow in the first two games would be automatically suspended for the next match in the elimination rounds if he gets another.

A red card? Even worse. That results in immediate removal from the match, automatic suspension from the next match, and possible further discipline if the foul is determined serious enough.

But there's a lifeline and some breathing room for teams who are already through to the next round. Stay clean in these final group matches and players carrying yellow cards from the early games will have their record wiped clean for the start of the elimination rounds.

How to earn a yellow card or red card

A yellow card is a warning for a range of fouls including reckless challenges, wasting time, excessive celebrations and arguing with game officials. Persistent fouling or denying a goal-scoring opportunity in the penalty area is another quick way to earn a yellow card.

A lot is left to the referee's discretion in the heat of play.

Red cards are more rare and usually result from more serious penalties, such as dangerous tackles, violent play, spitting, biting, offensive language and denying a clear goal-scoring opportunity.

A new rule this year allows a red card if a player covers his mouth to disguise what he says during a confrontation with another player. That happened to Paraguay midfielder Miguel Almiron in the second round.

A player who earns two yellow cards in a single game also results in a red card, and they are sent off and suspended for the next match.

Accumulated yellows raise a big question: To play or not to play

The yellow card/red card factor can become a dilemma for coaches. A team still fighting for a spot in the next round will need its best players on the field even if they have a previous yellow card.

Coaches of teams already through to the next round are more likely to sit players with yellow cards on their record.

The U.S. had four starters who earned yellow cards in the first two matches, including two earned by striker Folarin Balogun and defender Chris Richards late in the Americans' 2-0 win over Australia.

“It’s unnecessary to take a risk to pick up another yellow card and not be available for the next round," Pochettino said Wednesday.

Other top teams with multiple players carrying yellow cards into their final group matches include Portugal (four) and the Netherlands (three).

Teams get extra amnesty this World Cup, but the cards can also be tiebreakers

The expansion of the World Cup this year from 32 teams to 48 created more games and more chances a player can earn yellow and red cards.

Because of that, FIFA created two “amnesty” periods for accumulated yellow cards. The first comes after the group stage, the second comes after the quarterfinals.

And the expanded tournament means several third-place teams will advance out of the group stage. And buried deep in the tiebreaker system is a team's “conduct score” that takes into account accumulated yellow and red cards. Too many will risk getting eliminated from the tournament.

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