Borys
Statistics Wizard
I decided to get a closer look at Match Stats just for my own interests, but migh as well post it here if anyone is interested. I will try to do it for the next couple of weeks and see if we can get some interesting conclusions which are contradiction to common knowledge - which data analysis is for.
THE POINT OF THIS THREAD is to confront the popular views which are considered as "obvious" with data and compare those phenomenons with other teams/ different combinations/ different players. Please restrain from posting cliché like "I don't need stats to see we're shit/ the only thing that matters is the league table" - this is not why we're here.
I am basing my analysis on WhoScored (players stats, heatmaps etc) and Understat (xG/xGA Timing Chart) mostly. Will keep OP updated if I find something new and interesing. Most of the general stats I take from fbref.
What is xG?
Expected goals (xG) measures the quality of a shot based on several variables such as assist type, shot angle and distance from goal, whether it was a headed shot and whether it was defined as a big chance. Expected assists (xA) measures the likelihood that a given pass will become a goal assist. It considers several factors including the type of pass, pass end-point and length of pass.
If you see that chance is described as having an xG rating of 0.1 that means a player would be expected to score from the chance 10per cent of the time - a one in ten chances (for example a header from a corner). If a chance is described as 0.5xG it should be scored 50% of the time (for example a easy one on one chance).
If you sum those parameters for each goalscoring situation, you get a Timing Chart. The cummulative value will be the final xG - the higher the more likely team is to score goals. Depending on final xG for opposition team, the delta should be a good indicator of what would be the score, not including converting chances parameter.
This graphs shows that our best period came in the second half, when WBA couldn't create anything.
So for example, lets compare two extreme cases - West Bromich Albion game and Brighton in EPL.
We've won WBA game and I thought we were quite unlucky not to score more goals. But it doesn't seem like a popular reaction on Redcafe as most people are moaning about lucky win. So was it a lucky win? We've had a Total xG score 2,43. So lets assume if we played that game 100 times, the average goals scored would be 2,43. At the same time, xG for WBA was at the level of 0,44, which means we would win most games by 2 goals. Based on that data, it seems we were quite unlucky not win by a higher margin. In the end we've scored only one goal (penalty), which can be explained by worst conversion rate in the EPL.
Now lets see the Brighton game, which we've won 3-2. I thought we were extremely lucky to get away with any point from that game, so I looked up the stats and guess what - we got a total xG score of 1,58 compared to Brighton 2,98. So basing on the number and quality of chances we've got, we should be losing that game by at least one goal (graph below). We've also made a total number of 3 shots on target (scored 3), compared to 7 vs WBA. If we played that game multiple times, we would concede 3 goals on average so quite lucky on that end too.
THE POINT OF THIS THREAD is to confront the popular views which are considered as "obvious" with data and compare those phenomenons with other teams/ different combinations/ different players. Please restrain from posting cliché like "I don't need stats to see we're shit/ the only thing that matters is the league table" - this is not why we're here.
I am basing my analysis on WhoScored (players stats, heatmaps etc) and Understat (xG/xGA Timing Chart) mostly. Will keep OP updated if I find something new and interesing. Most of the general stats I take from fbref.
What is xG?
Expected goals (xG) measures the quality of a shot based on several variables such as assist type, shot angle and distance from goal, whether it was a headed shot and whether it was defined as a big chance. Expected assists (xA) measures the likelihood that a given pass will become a goal assist. It considers several factors including the type of pass, pass end-point and length of pass.
If you see that chance is described as having an xG rating of 0.1 that means a player would be expected to score from the chance 10per cent of the time - a one in ten chances (for example a header from a corner). If a chance is described as 0.5xG it should be scored 50% of the time (for example a easy one on one chance).
If you sum those parameters for each goalscoring situation, you get a Timing Chart. The cummulative value will be the final xG - the higher the more likely team is to score goals. Depending on final xG for opposition team, the delta should be a good indicator of what would be the score, not including converting chances parameter.
This graphs shows that our best period came in the second half, when WBA couldn't create anything.
So for example, lets compare two extreme cases - West Bromich Albion game and Brighton in EPL.
We've won WBA game and I thought we were quite unlucky not to score more goals. But it doesn't seem like a popular reaction on Redcafe as most people are moaning about lucky win. So was it a lucky win? We've had a Total xG score 2,43. So lets assume if we played that game 100 times, the average goals scored would be 2,43. At the same time, xG for WBA was at the level of 0,44, which means we would win most games by 2 goals. Based on that data, it seems we were quite unlucky not win by a higher margin. In the end we've scored only one goal (penalty), which can be explained by worst conversion rate in the EPL.
Now lets see the Brighton game, which we've won 3-2. I thought we were extremely lucky to get away with any point from that game, so I looked up the stats and guess what - we got a total xG score of 1,58 compared to Brighton 2,98. So basing on the number and quality of chances we've got, we should be losing that game by at least one goal (graph below). We've also made a total number of 3 shots on target (scored 3), compared to 7 vs WBA. If we played that game multiple times, we would concede 3 goals on average so quite lucky on that end too.
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