The Importance of the Away Goal

“Always hated the away goal rule, kills so many games” Gary Lineker supported a year ago, unable to tolerate the knockout of Manchester City from AS Monaco after they drew 6-6 on aggregate in the last-16 phase of the UEFA Champions League. Many fans across the world have adapted Lineker’s opinion, stating that no goal should be of greater value. On the other hand, others believe that criticism over the away goal rule ignores the moments of excitement that it provides. Nevertheless, one thing is certain. The away goal rule has a tremendous impact on a team’s approach to the game.

Abstract

The purpose of this research is to focus on the correlation between away goal and success  in knockout games. The importance and the specific weight of an away goal are analyzed along with its effect on a team’s progress. In accordance, this report will give an insight about each country’s ability to perform well in home and away matches and whether small differences in ranking affect the total number of scored goals in such clashes.

Collection of Data and Analysis

The competition under which the significance of the away goal will be evaluated is the UEFA Champions League, probably one of the most recognized and highly anticipated tournaments in football and sports in general. Data was collected from the later stages of the competition (quarter and semi-finals), as in earlier stages big differences in coefficient ranking and performance in the group phase were considered as important factors that could not be neglected.

The Away Goal in Numbers

First of all, it is essential to check the actual impact of the away goal rule in the later stages of the UEFA Champions League. Surprisingly, only 12.2% of pairs competing against each other for a place in the final or the semi-finals have been determined from the away goal rule. But does that mean that the away goal has such a small impact?

The answer would be positive only if the direct application of the away goal rule was taken under consideration, which is the determination of the winner in home and away games that end as a draw on aggregate. However, this is not the case in this research. One can consider the away goal as a game changer due to the fact that most in-game alterations, such as substitutions or changes in the formation, highly depend on it. It even has the indirect ability to alter the approach and the tactical plan of a game or a series of games before they even start.

A possible example is the mentality of the home team in the first match of a knockout phase. The coaching staff usually makes its decisions depending on limiting the possibilities of conceding an away goal. Actually, in many cases managers prefer having a clean sheet to winning the match but with the expense of conceding an away goal. This is depicted in the number of teams that progress to the next round after reassuring a clean sheet in the first match; a number surpassing 70%.

 

 

The significance of the away goal could be also highlighted from the scope of the visiting team. Teams that manage to convert their chances into a goal in the first leg of a knockout series, despite the result at the end of the match, have more than 50% possibilities to pass to the next round. Analogously, almost 80% of teams scoring exactly 2 away goals in the first game would succeed in progressing further to the competition, while hitting the net 3 times or more will undoubtedly define them as early winners in this clash.

Strength Correlation

To continue, another interesting part would be to analyze whether small variations in rankings between two clubs competing each other for a place in the semi-finals or even the final, affects the overall number of away goals scored. In addition, in this part of the analysis seasons 2002/2003 and 2003/2004 were not evaluated in the final outcome.

For the interpretation of results the researcher performed a chi-squared test. The chi-squared test use is to determine if there is a significant difference between the expected frequencies and the observed frequencies in one or more categories. The two factors in this report are ranking, as presented annually in the official site of UEFA, and goal width. Ranking categories consist of 4 integrals:

1. [1-4]
2. [5-13]
3. [14-25]
4. [26+]

Accordingly, total away goals were categorized in three intervals:

i) [0-2]
ii) [3-4]
iii) [5+]

The Null Hypothesis in this report is that ranking coefficients of teams do not play a role in their scoring abilities, with a confidence interval of 0.9.

The results from the chi-squared test indicate that our initial assumption is false; P-value is approximately 0.097; hence the null hypothesis is rejected. Rankings and number of goals appear to have a connection.

In order to determine the intensity of these connections, covariance calculations are used. Covariance is a measure of the joint variability of two random variables. If the greater values of one variable mainly correspond with the greater values of the other variable, the covariance is positive. It is concluded that the covariance between teams that lack at scoring away goals [0-2] and those that moderately do it [3-4] takes the value of 10.25, expressing a big similarity in behavior. In contrast, the covariance between teams insufficient in attack and teams that score a lot is -2.25, revealing a negative linear association between the two variables, while that between intervals ii and iii is around 0.18, declaring a rather small correspondence.

Nationality Inclination in the Knockout Phase

At this moment it would be interesting to analyze each country’s performance at the later stages of Champions League. Data was collected for the 90 pairs of this 15-year era, even though the final analysis contains only clashes between clubs from different nations. In this way, one can find out which country performs better in knockout matches, where pressure holds a crucial role in the overall outcome.

The map displays that Italy along with United Kingdom are inclined to succeed in this type of matches. Both of them reach almost 61% success rate in their confrontations with rival clubs. Premier league teams are likely to progress to the next round as they are keen on coming up against do-or-die games. English teams consolidate their presence to the quarter-finals, having the biggest number of appearances in the last 15 years.

Italian clubs, on the other hand, do not appear so many times in the later stages of the competition; however they are merely consistent and have the know-how to confront and overpass their opponents in such clashes.

Spanish clubs keep up with the above mentioned teams, having a success rate of 58.1%. This rate surged in the last 4 years as all former winners of the tournament come from this country. Furthermore, compared to Portugal and the Netherlands (success rate of 28.6% and 25% respectively) Germany is performing well in knockout matches, as German teams manage to score an efficient number of away goals. Nevertheless, they are not the force they used to be, thriving in only half of their total confrontations, and undoubtedly not preserving Lineker’s another famous quote: “Football is a simple game; Twenty-two men chase a ball and at the end the Germans always win”.

Summary

Overall, it seems that away goals have an enormous impact for a team on progressing and  succeeding in a competition. Clubs from Italy and United Kingdom have more chances to take advantage of the away goal and prosper. Finally, strength variation among the teams could highly influence the total number of away goals.


Bibliography

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UEFA.com. (2018). Member associations – UEFA rankings – Club coefficients – UEFA.com. [online] Available at: https://goo.gl/QfPDwi [Accessed 25 Jan. 2018].

Statistics How To. (2018). Chi-Square Statistic: How to Calculate It / Distribution. [online] Available at: https://goo.gl/vukPAi [Accessed 25 Jan. 2018].

Statistics How To. (2018). Chi Squared Table (Right Tail). [online] Available at: https://goo.gl/b2gPV7 [Accessed 25 Jan. 2018].

Transfermarkt.com. (2018). Football transfers, rumours, market values, news and statistics. [online] Available at: https://goo.gl/PDywZA [Accessed 25 Jan. 2018].

As an engineer I have learned that it is not only about deriving the result but also explaining it. In Statathlon I found the unique opportunity to combine mathematics with my other passion, football, and strive to describe the phenomena that rule it.

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