Network science reveals the secrets of the world’s best soccer team

Emerging Technology from the arXiv, Network science reveals the secrets of the world’s best soccer team, Oct 4, 2019.

One of the best soccer teams in history is widely acknowledged to be the Barcelona side that played during the 2009-10 season. Under the inspirational leadership of manager Pep Guardiola, this team won six major competitions including the Spanish football league, known as La Liga, and the UEFA Champions League, the most prestigious competition in world football. No other team has accumulated so many trophies in such a short period.... 

Using network science to study sports is a relatively recent approach. The idea is to represent each player in a team as a node and create a link between players whenever they pass to each other. As the number of passes increases, the link becomes stronger. The data also includes the position of each player when a pass is made. By the end of the game, this network is a powerful record of the links between players and the way the game has evolved. 

But much more is possible: researchers in other disciplines have used network science to study the internet, the spread of disease, forest fires, and even the emergence of war. Sports scientists can use these powerful mathematical tools to analyze the nature of a team’s network and the most important nodes within it. 

Various researchers have already applied this approach to football. They have found that the networks form “small worlds” (in other words, it is possible to cross the network in a much smaller number of links than there are players in the team); that certain players are more “central” than others (in other words, the ball is much more likely to be passed to and from them); and that certain patterns of play, or “motifs” are common, such as playing the ball between three players forming a triangle.... 

They first generate passing networks for both teams in every La Liga game played in the 2009-10 season. That’s 380 games played between the 20 teams in the top tier of the Spanish national league. 

They then calculate a number of well-understood network features for each team. These measures included the clustering coefficient, which describes how well triplets of players pass to each other and is much higher for Barcelona than any other team; the average shortest path through the network, which describes how well the ball is passed across the team and is much shorter for Barcelona than any other team; and the largest eigenvalue of the connectivity matrix, which measures the strength of the network and is higher for Barcelona than any other team. 

Buldú and colleagues look at how the network evolves over time using the 50-pass networks. “We are able to identify those network metrics that enhance the probability of scoring/receiving a goal, showing that not all teams behave in the same way and how the organization Guardiola’s F.C. Barcelona is different from the rest,” they say....

The ratio of advance measures how likely the team is to pass forwards, backwards, or horizontally across the pitch. Again Barcelona is unusual, in that its passes are more likely to be horizontal than any other team’s. This reflects the strategy of passing the ball back and forth across the pitch looking for opportunities to attack. 

Barcelona also has the highest centrality of a single player in Xavi, who is widely acknowledged to have been one of the best midfielders of all time.