When can a fourth substitute be used at the World Cup 2018, and when did the rule start?
New rules from FIFA have changed the way managers can utilise their huge substitute benches during the World Cup
We all know the benefits of the super sub.
Fresh legs from the bench can turn a game one way or the other, and now bosses are being given an extra substitution in World Cup knockout games.
When can a fourth substitute be used at the World Cup 2018?
If a game goes to extra-time, World Cup bosses will get the option to use a fourth substitute.
Fifa have brought in the ruling for the first time after successful trials in domestic competitions over the past two years.
During his Real Madrid days, Alvaro Morata became the first fourth substitute ever in the men's game when he was brought on for Cristiano Ronaldo during extra-time of the 2016 Club World Cup.
Eager to push forward with the idea, a fourth sub will be available during extra time at Champions League and Europa League knockout rounds from next season.
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Mario Gotze famously entered the field in Rio as an 88th minute substitute, moments before the final went to extra-time - and went on to strike the winner.
Under the new ruling, managers can wait until the added 30 minutes and use another set of fresh legs from their 12-man benches.
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