The away goals rule
Virtually all football fans have heard of the away goals rule. As you would know, knockout matches in the UEFA Champions League (apart from the final) take place as two-legged ties. In the case of a draw after 180 minutes, the team which has scored the most goals away from home progresses to the next round: this the ‘away goals rule’.
Countless UCL knockout matches have been settled by the away goals rule (sorry City fans, no salt intended). It is absolutely central to the thinking of players and managers alike during a knockout match. A goal scored away can be worth almost twice its weight in gold, and a goal conceded at home can be almost twice as painful. Managers set their teams up to be able to score away from home and take more risks, and be more defensive at home.
The rule has been described as being “unfair…illogical, and often achiev(ing) the opposite of what it’s supposed to do”. But this piece does not seek to weigh the away goals rule against all the proposed alternatives such as penalty shootouts. It seeks to establish that there is no decisive a priori reason why there should be an away goals rule instead of a home goals rule: in fact, there is a strong case that a home goals rule should be preferred.
The away goals rule seems to reflect a historical preference towards encouraging offensive play away from home. It was originally introduced in order to mitigate the difficulty of obtaining an away win. A goal scored away from home is objectively more difficult, and has especially been the case in the past. Players need to play on an unfamiliar pitch, often in an unfamiliar country. Transport is cumbersome. The crowd will boo you non-stop. Thus, it seems intuitive for the more objectively difficult task to be rewarded: if you have scored more goals away from home, the better a feat you have achieved, and so this means you deserve to prevail in the case of the scores being level.
Turning logic on its head?
However, this logic ignores the fact that we can reach the opposite conclusion, viewed from a defensive perspective. Just as it is objectively more difficult to score away from home, it is also more difficult to concede fewer goals away from home. If we decide to reward the more difficult task from a defensive perspective in the case of a tie, we can say that the team which concedes the fewest goals away from home prevails.
Rewarding the team with the fewest goals conceded away from home is the precise polar opposite to the away goals rule: it is a ‘home goals rule’. Let’s take the Champions League quarter-final tie between Spurs and City. Spurs won 1-0 at home, and lost 4-3 at the Etihad. The scores were level at 4-4 at the end of the tie, and Spurs went through because they managed to score 3 goals away from home, while City scored 0. On the logic of the away goals rule, Spurs deserved to go through because it is objectively more difficult to score an away goal, and Spurs scored 3 away from home in contrast with City’s 0. But can’t it also be said that it is objectively more difficult to concede 1 goal away from home (as City did), as opposed to 4 (as Spurs did)? If we reward the objectively harder task, City should have progressed. This is a ‘home goals rule’ because if the scores are level, conceding fewer goals away from home necessarily means scoring more goals at home.
One may take issue with the fact that the comparators involved in ascertaining the ‘objectively harder task’ (goals scored away v goals scored at home; goals conceded away v goals conceded at home) are internalised within the metrics of ‘goals scored’ and ‘goals conceded’. It is more difficult to score away from home than it is to score at home. Likewise, it is more difficult to concede fewer goals away from home than it is to concede fewer goals at home. Each comparison is hermetically sealed within its respective silo of ‘offensive performance’ and ‘defensive performance’ respectively: they do not interact with each other.
Yet, does this mean that the away goals rule is privileging offensive football, at the expense of defensive football? No, as will be seen below.
Rewarding attacking and defending in equal measure
It is only one part of the picture to say that ‘given that an away goal is worth more, the incentive is to attack away from home’: it only privileges offensive football to this extent. The other side of the coin cannot be ignored: because it is more costly to concede an away goal at home, the away goals rule also privileges defensive football by rewarding the team which concedes fewer goals at home. It rewards offensive and defensive performances in equal measure.
The same principle applies if the ‘home goals rule’ were to be adopted. If it is worth more to score at home, this rule privileges offensive football at home. The corollary of this is that it privileges defensive football away from home since the rule rewards the team that concedes fewer goals away from home.
Is there any practical difference if one rule is adopted over the other? Yes, but only one. This has only one consequence in terms of the incentive that the rule creates for the offensive and defensive players respectively. If the away goals rule is retained, this means that offensive players are encouraged to be more familiar with different types of pitches (since away goals are worth more), while defensive players are encouraged to know their own pitch like the back of their hand (since it is more damaging to concede a home goal). Conversely if the home goals rule is adopted, the positions are reversed: it is the offensive players who are encouraged to be familiar with their own pitch (since home goals are worth more), and it is the defensive players who are encouraged to be familiar with other pitches (since away goals conceded are more damaging). One may think that ‘familiarity with pitches’ is a negligible concern, but (as an extreme example) Klopp has shown otherwise in his remonstrations against Cardiff’s ‘dry pitch’.
The ‘home goals’ rule and attacking football
Which incentive structure is more desirable? This depends on what you value in football. The general public seems to want to see displays of attacking football: one needs to look no further than the comparison between the Manchester United in the Sir Alex Ferguson days as opposed to the Manchester United in the Jose Mourinho days.
If attacking football is thought of as being at the core of an entertaining display, there is a strong case for the home goals rule to be adopted. With the current away goals rule, it does not fare as well in terms of promoting attacking football. Teams are more wary of conceding at home, and thus become more defensive. This is in addition to the fact that it is comparatively easier to defend on one’s own pitch, generally leading to better defensive performances. At the same time, it is harder for the away team to score, given the different conditions: all these factors point towards players and coaches being very defensively-minded, fostering the occurrence of dull games. However, if the home goals rule were to be adopted, the incentives would be reversed. Teams would be incentivised to score more at home, and it would be easier for them to score given the home advantage, especially with a familiar pitch. Aligning the incentives (to attack at home) with the easier task (attacking at home) will conduce to more attacking performances. On the defensive side, teams would be wary of conceding goals away from home, but it is objectively harder to defend well on an unfamiliar pitch. These factors point towards there being more offensive football.
Furthermore, although Champions League matches are now broadcasted, football needs to reward fans who go to the stadium live by increasing the likelihood of them enjoying the spectacle of attacking football, especially the local fan who decides to go to his home stadium when he can very plausibly watch the match on TV from the comforts of his couch. If a home goals rule were to be adopted, fans would be able to witness more attacking football, live: having more intense emotions as a result of the rule, and having those emotions amplified by being there in real life.
If attacking football is what you want to see, you would benefit more from a home goals rule than you would from an away goals rule.
There is one exception, however: all of this becomes moot if AC Milan and Inter Milan end up playing a knockout tie at the San Siro.
 If there is still a tie, the game is to be decided by a penalty shootout, but shootouts have been rare as compared to draws settled by the away goals rule