Which action by a player warrants a red card?

A player warrants a red card for serious foul play because this type of offense involves a reckless or excessive challenge that endangers the safety of an opponent. Serious foul play is considered one of the most severe actions on the field and is taken very seriously by referees to maintain player safety. When an action is deemed to fall under serious foul play, it indicates that the player has demonstrated a complete disregard for the opponent's well-being, which can lead to a direct dismissal from the game with a red card.

While unsporting behavior might be a cautionable offense, serious foul play crosses the line into actions that warrant immediate expulsion from the match. The same applies to a second caution for the same offense, which leads to a red card but is more indirect because it requires prior offending behavior. Time-wasting, while a concern, typically results in a caution, not an expulsion, unless it becomes excessively blatant alongside other factors in the match.