Regularized Adjusted Plus-Minus Models for Evaluating and Scouting Football (Soccer) Players using Possession Sequences

TL;DR

This paper introduces a new regularized adjusted plus-minus model for soccer player evaluation that leverages possession sequences to distinguish on-ball and off-ball contributions, offering nuanced player ratings.

Contribution

The paper develops a novel framework using possession sequences and four penalization schemes to improve player evaluation in soccer, accounting for positional and strength groupings.

Findings

The models effectively differentiate on-ball and off-ball player contributions.

The framework provides detailed player ratings for La Liga 2017/18 season.

Guidelines for practitioners on model selection and application.

Abstract

This paper presents a novel framework for evaluating players in association football (soccer). Our method uses possession sequences, i.e. sequences of consecutive on-ball actions, for deriving estimates for player strengths. On the surface, the methodology is similar to classical adjusted plus-minus rating models using mainly regularized regression techniques. However, by analyzing possessions, our framework is able to distinguish on-ball and off-ball contributions of players to the game. From a methodological viewpoint, the framework explores four different penalization schemes, which exploit football-specific structures such as the grouping of players into position groups as well as into common strength groups. These four models lead to four ways to rate players by considering the respective estimate of each model corresponding to the player. The ratings are used to analyze the 2017/18 season of the Spanish La Liga. We compare similarities as well as particular use cases of each of the penalized models and provide guidance for practitioners when using the individual model specifications. Finally, we conclude our analysis by providing a domain-specific statistical evaluation framework, which highlights the potential of the penalized regression approaches for evaluating players.