Manchester City host Real Madrid in the second leg of the Champions League semi-final tonight.
The scores are locked in at 1-1 after a thrilling opening game at the Santiago Bernabeu, with Pep Guardiola's side hoping that a home crowd can spur them on against the undisputed kings of European football.
In previous years, that one goal by Kevin de Bruyne in Madrid may have proved crucial in tonight's leg. In the past, teams have gone through despite drawing the fixture on aggregate, because they scored more away goals.
That's the way it had been for over half a century, and was first introduced in the 1965 Cup Winners Cup. The ruling has since been adopted by a huge amount of knockout tournaments globally. It was brought in to remove the need for a tie-breaker at a neutral venue and to encourage teams to attack away from home.
However, away goals no longer count in the Champions League.
The ruling was abandoned by UEFA back in 2021, meaning the Champions League, Europa League and Europa Conference League no longer have the ruling in place.
UEFA president Aleksander Ceferin said: "The impact of the rule now runs counter to its original purpose as, in fact, it now dissuades home teams - especially in first legs - from attacking, because they fear conceding a goal that would give their opponents a crucial advantage."
Over the years, the ruling was actively criticised by football's elite minds. Arsene Wenger branded it outdated, after his Arsenal side lost to Monaco in 2015 thanks to away goals.
"This rule was created in the 60s to encourage teams to attack away from home, but football has changed since the 1960s and the weight of the away goal is too big today."
If Man City and Real Madrid draw on aggregate tonight, the game will go straight to extra-time, and then penalties if the stalemate is not broken.
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