Abstract
The aim of this study was to define a method for evaluating a player’s decisions during a game based on the success probability of his actions and for analyzing the player strategy inferred from game actions. There were developed formal definitions of i) the stochastic process of player decisions in game situations and ii) the inference process of player strategy based on his game decisions. The method was applied to the context of soccer goalkeepers. A model of goalkeeper positioning, with geometric parameters and solutions to optimize his position based on the ball position and trajectory, was developed. The model was tested with a sample of 65 professional goalkeepers (28.8 ± 4.1 years old) playing for their national teams in 2010 and 2014 World Cups. The goalkeeper’s decisions were compared to decisions from a large dataset of other goalkeepers, defining the probability of success in each game circumstance. There were assessed i) performance in a defined set of classes of game plays; ii) entropy of goalkeepers’ decisions; and iii) the effect of goalkeepers’ positioning updates on the outcome (save or goal). Goalkeepers’ decisions were similar to the ones with the lowest probability of goal on the dataset. Goalkeepers’ entropy varied between 24% and 71% of the maximum possible entropy. Positioning dynamics in the instants that preceded the shot indicated that, in goals and saves, goalkeepers optimized their position before the shot in 21.87% and 83.33% of the situations, respectively. These results validate a method to discriminate successful performance. In conclusion, this method enables a more precise assessment of a player’s decision-making ability by consulting a representative dataset of equivalent actions to define the probability of his success. Therefore, it supports the evaluation of the player’s decision separately from his technical skill execution, which overcomes the scientific challenge of discriminating the evaluation of a player’s decision performance from the action result.
Highlights
In team sports, players’ decisions are determinants of the team’s performance
Formal definitions for i) the stochastic process of the player decision in game situations and ii) the inference process of the player strategy based on his game decisions were developed
player strategy (PS) presented better performance than player’s decision model (PD) for the two goalkeepers in all xi, evidenced by the fact that the goalkeepers’ PS performance corresponded to the oracle’s lowest value. These results indicated that the theoretical framework that led to the formulation of PD and PS enabled the computation of the optimal goalkeeper strategy based on the available oracle
Summary
Players’ decisions are determinants of the team’s performance. The control of any action execution has been modeled by a set of action rules of the following form: if [1]. According to this model, each player has a list of action rules available. Each player has a list of action rules available They are strategically defined by the coaching staff, considering the actions a player should perform in each game circumstance. A player executes an action related to his list of action rules when his prediction of the game state matches that action condition. Since an ill-conceived and well-executed action usually results in an unsuccessful outcome, it is important to analyze the decision that led to the action, its execution
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