Does a “clutch” goal scorer exist in the EPL? A player who seems to always score goals when the team needs them most. A player who, when the game is on the line, steps up and finishes. This is, of course, a tough question to answer. How do we even define a “clutch” moment? Is a game winning goal in the 90th minute more clutch than a tying goal in the last game of the season? Is a goal to go ahead by 3 in the 70th minute more clutch than a goal to cut the opponent’s lead to 2 in the 35th minute?
To start to quantify these questions, I have created an outcome probability calculator on my blog, Soccer Statistically. This calculator allows you to input the venue, minute, and goal differential of the game. Based on these inputs, you the team’s chance of winning, drawing and losing are given to you. These percentages are calculated based on historical EPL data. Basically, I aggregated EPL game data from previous seasons, and calculated a percent chance of the team winning, losing and drawing in every game situation. Overall there are 90 x 2 x 7 = 1260 of these situations in a game. In some situations, the percentages stray from the nice trend which is exhibited for the rest of the game. To solve this problem, I regressed over the data to create nice trend lines which extrapolate in instances when there is not enough data. This allows us to have an outcome probability for every situation. If you want to try out the calculator yourself, here is a link.
So what does this have to do with clutch goal scoring? Using these outcome probabilities, I am able to quantify the true value of each goal. The problem with ranking goal scorers just based on the number of goals they have scored is that it values each goal equally. Why should the game winning goal in the 90th minute be valued the same as the 5th goal in a 5-0 win? They clearly do not have the same value to the team. To solve the problem I created a metric called Expected Points Added, which weights each goal based on the probability it adds to the team winning. To simplify matters, I multiplied each probability by 3 to instead get the points added, which is a little easier to understand in my opinion. This way, the go ahead goal, at home, in the 34th minute is worth .87 expected points because it increases the team’s expected points by .87. Similarly, the tying goal, away, in the 65th minute is also worth .87 expected points. Each of these goals, although in very different scenarios, increase a team’s expected points by the same amount.
Now that I had a way to measure the true value of each goal a player scores, I was able to do this for every goal of the entire season and then re-rank the top goal scorers. This goal scorers list is ranked based on Expected Points Added, not goals. My list is similar to the actual top goal scorers list. However, there are many interesting changes. Some players, based on their goals, either underperform or over-perform when the weight of each of their goals is taken in to account. To measure this, I also created another metric called Average Goal Weight, which is just the player’s Expected Points Added divided by the number of goals they have scored. This measures how valuable, on average, the player’s goals have been this season. Players with a low Average Goal Weight could be seen as “overrated” based on just their number of goals scored, while players with a high Average Goal Weight could be seen as “underrated” based on their goal total.
Below is the table for the 25 players with the highest Expected Points Added this season:
On the Next Page: Analysis of the Expected Points Added – Top 25 list…
Some notable points:
- What sticks out the most to me is Wayne Rooney’s position. Despite scoring 21 goals this season, Rooney is ranked 7th when the importance of each goal is taken in to account. To put it in perspective, Rooney has added 7.80 expected points with his goals, while Grant Holt has added 9.38 expected points. This is despite the fact that Rooney has scored 10 more goals than Holt.
- It shouldn’t be a question that van Persie is leading this list. While he already leads in the number of goals scored, he has also scored a lot of crucial goals for Arsenal this season. His Average Goal Weight is .82, meaning on average, his goals are weighted as .82 expected points. If you consider the fact that a tying goal in the 90th minute is worth about 1 expected point, it is clear that RVP is scoring a lot of important goals.
- The highest Average Goal Weight in the top 25 goes to Frank Lampard, who ranks 5th on the list despite only scoring 10 goals. On average, his goals are worth a whopping .9 expected points.
- Manchester City’s Sergio Aguero has also not scored that many important goals. His Average Goal Weight is only .46, a little more than half of Lampard’s pace.
These are just a few points, but I’m sure you can find a lot of other interesting pieces of information from the chart. I encourage you to also look at a more extensive list on my blog here. This list is also updated weekly if you want to continue to follow the rankings throughout the rest of the season.
The Expected Points Added metric can give a lot of insights in to the true value of a goal scorer. However, I think it is important to point out a few caveats of the metric. First, it seems like this metric does not stay constant from year to year for specific players. For example, it doesn’t seem to be the case that certain players have consistently high Average Goal Weights from year to year. In other words, the metric is not necessarily predictive. However, EPA can still be a good insight in to the performance of a player within a specific season. Second, players like Aguero and Rooney might be getting punished in this measure because they both play for clubs that often blow teams out. For example, if Aguero scores the 5th goal in a 5-0 game (which would happen more often with clubs like United and City), he would receive no Expected Points Added for that goal because it is essentially worth nothing, as City would already have a 100% chance of winning the game. However, this goal would hurt his Average Goal Weight by bringing down the average. Should he really be punished for this? Maybe, maybe not, but it is just a part of how the metric works. Without it, we wouldn’t be able to gain the insights that the chart above provides.
Overall, I encourage you to stay updated on the Expected Points Added leaders on my blog. I’m also interested to hear reader’s thoughts on if a clutch goal scorer really does exist. It’s a tough question to answer, and there are a lot of different opinions on the subject.