The FA Cup is planning to introduce a rule that will allow teams to make a fourth substitution in extra time of the quarter-finals, semi-finals and final.
In conjunction with the IFAB - football's law-making body - the Football Association will test the new format in the 2016-17 competition.
The current rules state that teams can only use three substitutions from a bench of seven players, but now an additional member will be allowed to come on for a teammate during 30 minutes of extra time.
The news comes two months after it was announced that quarter-final replays have been scrapped, resulting in final-eight fixtures being decided in either extra time or penalties should the 90 minutes end in a stalemate.
FA chief executive Martin Glenn said: "The Emirates FA Cup is renowned for its great history and tradition but, as the game's governing body, it is important the FA continues to look at how it can further add to the drama and spectacle of a competition loved by millions around the world.
"With the Cup now adopting a straight knockout format from the quarter-finals onwards, the introduction of a fourth substitute in extra time will bring extra intrigue and interest.
"Also, from a technical point of view, it will be interesting to see how managers use the chance to make an additional substitution in such high-profile games and the impact it has on the final result. Player welfare and being mindful of the number of games people play at the elite level has also been a consideration."
The Copa America tested the format in their competition earlier in the summer.
