Showcase - Chelsea and Spurs, what's the difference?

For anyone that knows me you will be aware of my passion in the game of football and my keen interest in data. So I wanted to focus today's showcase on the Premier League title race (which is just about still alive). Unfortunately the team that I support (who I am not naming, but plays in Red and is not from Liverpool), is nowhere near the challenge this year. Chelsea are now 7 points clear with 8 games to play and based on their form and remaining fixture list it is highly likely that they will be League Champions at the end of May.


Why Chelsea and Spurs?

Having studied a fair amount of the football data this season I decided to focus on 2 teams for this post, Chelsea and Spurs. My rationale for comparing Chelsea and Spurs is not simply because they are in positions 1 and 2, they are also fairly close in certain key statistics such as goals scored, goals conceded and shooting accuracy. Obviously football games can be determined by individual brilliance so looking at the data for the season to date won't always translate into a league position, but after 30 games it should be a good indicator.


Goals scored and conceded

As of today the goal difference for both Chelsea and Spurs is the same, +38; Chelsea have scored 2 more goals than Spurs which obviously means that Spurs have conceded 2 less goals than Chelsea. You could equally argue that scoring goals is more important than defending goals and vice versa so not much can be concluded based purely on goals scored and conceded.


big chances created

A further statistic to look at is big chances created which Opta define as:

 "A situation where a player should reasonably be expected to score usually in a one-on-one scenario or from very close range." 

This statistic essentially measures creativity and based on this seasons data both teams are just above mid table in terms of this output. The 2 Manchester clubs create the most but this doesn't translate into the same effectiveness as Chelsea and Spurs. In the following chart you can drill down into the teams data by selecting the corresponding bar to view who is creating chances for their respective clubs.


Attacking Effectiveness 

So far, based on the statistics, there is very little to separate Spurs and Chelsea (apart from the obvious points difference in the league table). Next I wanted to look at Attacking Effectiveness (a metric that I found via @experimental361), which essentially analyses shots taken per game against shots per goal. So it will highlight if a team is taking a lot of shots but are ineffective in actually scoring them. 

There are a few interesting outliers in the below chart; Southampton (having a lot of shots but not converting them), Middlesborough (having very few shots per game and not effectively converting them - spells big trouble), Man Utd (same boat as Southampton) and West Brom (having very few shots per game but are highly efficient at finishing them). 

In terms of Chelsea and Spurs there is a bit of a gap in terms of shots and conversion of the shots. Chelsea have nearly 2 shots less per game than Spurs however they score 1 goal per 5 shots whereas Spurs score 1 goal per 6 shots. 


Shot Quality

Building upon the attacking effectiveness above, another statistic to look at is the shot conversion; the number of shots on goal (i.e. needs the goalkeeper to save the shot) per goal, this will highlight teams that are more effective at converting their chances.  

As you will see Chelsea have the second best rate (behind West Brom) whereas Spurs are 10th.

This is further reinforced when looking at expected goals (discussed in a previous blog post) where Chelsea have scored 61 goals whilst their expected goal statistic suggests that they should have scored 45 goals. In the case of Spurs they have scored 58 goals and expected goal statistic suggests they should have scored 48 goals. So Chelsea again have a clear advantage in this metric. The 2 Manchester clubs are underperforming in this statistic which validates the big chances created issue.


League over?

Chelsea are clearly in the driving seat and with only 8 games left it is unlikely that Spurs will be able to win the league, however there are positive signs for the North London side which might open opportunities for them. In the last 10 game weeks they are on a par with Chelsea in terms of the statistics that we previously discussed and they arguably have an easier remaining fixture list. We'll find out soon what will happen ....