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Now it is around the halfway stage of the season, its time to have a look at some stats. Everyone loves goals, so I am going to have a quick look at some of the top scorers from this season’s top 5 leagues in Europe (England, Spain, Italy, Germany and France). These stats have been produced thanks to the amazing website Understat which is an incredible website I would highly recommend for anyone looking for advanced stats.
What I am looking at here is players who have scored 10 or more non-penalty goals this season. The reason I have gone for this is penalties don’t really show who is the better striker.
Lets open this up with the first chart. This one is Non-Penalty Goals (NPG) v Expected Non Penalty Goals (xNPG). This shows who is over performing and who is under performing depending on how good the chances they have had. For those of you who aren’t overly familiar with Expected Goals, Understats description is:
Expected goals (xG) is the new revolutionary football metric, which allows you to evaluate team and player performance. In a low-scoring game such as football, final match score does not provide a clear picture of performance. This is why more and more sports analytics turn to the advanced models like xG, which is a statistical measure of the quality of chances created and conceded. Our goal was to create the most precise method for shot quality evaluation.
For this case, we trained neural network prediction algorithms with the large dataset (>100,000 shots, over 10 parameters for each).
As you can see from here, it comes as no surprise that the top scorer this season is Lionel Messi with 16 goals. This is impressive considering his xG value is only 10.81. Most of the top strikers will outperform their xG but this chart shows a couple of noticeable exceptions, Mo Salah, Luis Suarez, Sergio Aguero and believe it or not, Cristiano Ronaldo (more on him later).
What I would say about those four is that they are getting into good positions but just not taking their chances. This could easily change in the second half of the season.
The next chart I am going to look at is Non-Penalty Goals per 90 Minutes (NPG90) v Expected Non-Penalty Goals per 90 Minutes (xNPG90). This now takes into account the amount of time spent on the pitch rather than just total of goals.
What you can see from here is the big jump for Paco Alcacer. Alcacer has been scoring plenty of goals for Borussia Dortmund this season but the majority of them have come off the bench. If he starts more games for Dortmund, I would expect to see this figure drop considerably. A lot of his goals come late in games where Dortmund can catch teams on the counter attack and also a fresh striker like Alcacer can be deadly against tired defenders. At the other end of the table is Harry Kane who is averaging 0.52 goals per 90 minutes, which is what you would expect a top player to score (basically a goal ever other game).
This next chart is an interesting one. It is the expected goals total for all goals that were scored. Only shots, headers etc that were scored count here. I looked into this to see who was scoring the best chances. This is one for discussion, what makes a better striker? Someone who can score the harder shots, or someone who gets consistently into great positions in the box. Let’s have a look at the chart.
This has been sorted into order by the expected goals total. What you can see here is it Mbappe and Messi are leading the way. While I wouldn’t call them penalty box strikers, a lot of their goals are scored from close range but that is because of their abilities to dribble past defenders in the box. Down at the far end is Florian Thauvin, who has put his poor spell at Newcastle behind him and is on fire in his homeland this season. Thauvin has shown how dangerous he is by cutting in on his left foot from the right wing.
The next chart carries on from the previous one. This is the average expected goals value of each goal they have scored this season.
From here you can see that Messi’s number of goals knock him down a bit whereas Mo Salah and Cristiano Ronaldo jump right up there. To put things into perspective here usually the average xG of a shot is 0.12-0.14. So, these top strikers are getting into great positions when they are scoring goals.
The final chart focuses on shots. In this chart you will see Total Shots, Shots Per 90 Minutes and Expected Goals Per Shot.
This perhaps shows why some of Ronaldo’s stats are skewed a bit, the guy takes a ton of shots! He has taken 43 shots more than the second highest player. Also, a lot of his shots have been long range, which is why his expected goals per shot value is so low, compared to someone like Luis Suarez or Paco Alcacer. As you can see below at Ronaldo’s shot map, the majority of his shots are from outside the area (the green dots are the goals, only one of them is outside the box), most of these shots are only 0.01-0.04 in xG value. I know I shouldn’t be giving advice to one of the greatest players who ever lived, but serious Ronaldo, stop the long shots!!!
So what conclusions can we get from the about stats and charts? Well the main thing is the top strikers are really, really good. Some players in the second half of the season will improve. Mainly Aguero, Suarez, Ronaldo and Salah. They actual goals scored is currently below their expected goals value. Top strikers like that will usually always end up with a higher goals scored total than expected goals. What may also happen in the second half of the season is some players who have had really good starts to the season, will see their xG total and their actual goals scored total get closer, I’m looking at players like Alcacer, Sala and Aspas.
The old adage of the great striker is someone who averages a goal every two games may have to be looked at. As we can see from the NPG90 chart, there are a lot of players scoring well about 0.50 goals per 90 Minutes, and getting close to a goal per game.
Some obvious things were shown and confirmed. Players will score more goals from better chances, not exactly ground breaking information though. Obviously, while its great to see a 25 yard screamer into the its not something that happens often enough to make a big difference in strikers. Again, from our shots chart, it shows that quality of chances rather than quantity is more effective.
Hopefully you have enjoyed this quick article, I’m looking to do more of these over the coming months. I will for sure be doing a similar article to this at the end of the season to see how things compare. I am also looking at doing an article on Expected Assists shortly, as this is a very interesting area of the game which stats can tell some hidden stories.
I’ll also hopefully do a follow-up article to this soon talking about how this particular data can be applied to betting on goalscorers.
