This is a review of the weighted plus/minus soccer metric research conducted by Steven R. Schultze and Christian-Mathias Wellbrock.
While soccer is the most popular sport in the world, its’ analytics have not reached the same level as those for other sports. However, the field is continuing to grow. A plus/minus metric has traditionally been considered too unwieldy and difficult for soccer due to the complex nature of the game. The plus/minus metric discussed here would be used to evaluate player performance and show whether a player’s presence on the field has a positive or negative effect. It also allows for a comparison regarding which players provide the greatest positive influence on the team.
The weighted plus/minus metric proposed by this research actually extends the data provided by the statistic in other sports. It takes into account the importance of the goal – a goal that wins the game is significantly more valuable than a goal that puts a team up 4-0. It also takes account the strength of the opponents, as defeating a strong opponent should have a higher weighting than defeating a weaker opponent. Variables taken into account in the calculations are game number, opponent, time, shot taker, shot result, and shot type. Each player’s time spent on the field was standardized to 90 minutes. This helps level out the playing field and eliminates bias between players who play many minutes every game versus those who play fewer minutes per game.
This weighted plus/minus statistic provides coaches and analysts with a quantitative evaluation of each player’s performance allowing for a comparison between players. It also provides coaches with insights in how training should be adapted for each individual player. During the scouting process, this metric would enable the comparison of players to help determine which player would be best suited for the team.
Another strength of the weighted plus/minus is its objectivity, allowing coaches to see which players are positively affecting team results and which are not. It also provides an objective basis for comparing players. This aides coaches when decisions need to be made regarding which players will play in an upcoming game given the strengths of the opponents. Coaches can use the weighted plus/minus metric to determine their opponent’s strengths and weaknesses in order to formulate the best defensive and offensive strategies that optimizes their chances of winning.
The weighted plus/minus statistic provides coaches and analysts with a more efficient method for evaluating players’ performance compared to traditional statistics and analyzing video.
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