A fourth substitute will be allowed if a game from the FA Cup quarter-finals onwards reaches extra-time, but what other game-changing rules have there been in the past?
The FA Cup is planning to allow a fourth substitution during extra time from the quarterfinals onwards as part of a test for a law change.
England manager Roy Hodgson believes the scrapping of FA Cup quarterfinal replays is the key to a Premier League winter break.
The Football Association has announced FA Cup quarterfinal replays will be scrapped from next season.
The dust has settled on Crystal Palace's FA Cup final agony but it doesn't seem to have made it any easier to take. If anything, it gets harder.
"You join a club like United to win these kinds of competitions and, when you do, it's a great feeling and hopefully we can relive it again and again"