Since 1965, home-and-away series in European club soccer tournaments have used goals scored on the road as the first tiebreaker should the teams finish with the same number of aggregate goals, the thinking being that away goals can be tougher to come by and thus should be rewarded. Plus, the tiebreaker allowed teams to avoid time-consuming third matches to break ties and was much more fair than arbitrary measures such as a coin flip, which for example was used to settle a 1965 European Cup quarterfinal series between Liverpool and Cologne after the teams played to three draws.
But in recent years, the away-goals tiebreaker has been the subject of some debate by coaches and fans who argued that the home team in the first leg of a series may play much tighter for fear of allowing a crucial away goal, giving the road team in that first game an unfair advantage, and that the away-goals tiebreaker was a relic of a time when road games were much tougher to play because of travel and inconsistency among field conditions and refereeing across Europe.