I have been thinking a lot about the relationship between left and right sided direct free kicks in addition to left and right footed free kicks. This was based on my previous finding that direct free kick conversation rates were not necessarily weighted equally across both sides of the pitch. To recap, this season so far shows that free kicks from the right are converted more than those from the left. So as promised, I have delved further into the data to explore.
For this analysis I extended my search to cover both direct free kicks scored and not scored, taken between the 10th of June and 3rd of October 2016, which gave me an extra 99 games and 6 goals in all.
Now to help understand left and right footed free kicks in the first instance, I split the pitch down the centre of the goal, to create a distinct left and right “side”. The first noticeable thing (perhaps somewhat expected) is the inverse relationship between pitch side and foot. For free kicks taken from the right side of the pitch, significantly more were scored with the left foot (72%) compared to the right (28%), whereas free kicks from the left side of the pitch were scored significantly more often with the right foot (85%) than the left (15%). Please see the graphic below:
This is further supported by the total attempts on goal, particularly from the right side. From the graphic below, we can see a relatively balanced proportion of left and right footed shots from the right side (44% and 56% respectively), but the conversion rate is greatest for shots with the left foot, as we can see from the figure above.
The natural curved trajectory that this inverse relationship creates may help explain this logic, but to really understand the relationship between left and right footed free kicks and conversion rates, we need to maximise the granularity of our StrataData. So let’s go back to our original pitch zones, which you may be familiar with from my first blog.
I used customised rectangles to find the number of shots that were taken in each zone, as well as the number of goals by both left and right foot. I then calculated left and right foot conversion rates for each zone, to find where on the pitch suits a right or left footed free kick taker. This is shown in the graphic below. In this image, I have subtracted the conversion rates to give the left/right foot difference, with the colour of the percentage value representing which foot had a greater conversion rate. So for instance, in zone F2, left foot conversion rate was 25%, whereas right foot conversion rate was 6%. Therefore, 25 minus 6 gives a 19% advantage for the left foot:
From the above graphic, it is clear that there are more blue than yellow percentage values, which essentially tells us that the left foot conversion rate is better than the right. Starting with zone 2 as a whole we see that in B2, left footed free kick conversion rates over right footed conversion rates is 18%. This follows the logic of the inverse relationship, but moving over to the equivalent left sided area (zone F2), we find the greatest conversion rate is still for left footed players (19% as left footed conversion rate is 25% versus just 6% for right footers).
This pattern follows suit across zone 2, with left footed free kicks converted more than right footed ones. The most prominent exception to this pattern is in zone F3, where once the direct free kick is moved slightly further away from goal, the right footed conversion rate is 9% greater than the left. To highlight the pattern of free kicks taken, scored and converted, I created a GIF, which should serve to highlight the potency of the left footer:
So what have we learnt? It seems that the left footed free kick taker is more lethal than the right, with greater left footed conversion rates spread across zones. Rectangle F3 on the left side of the pitch is the largest exception, as this seems to suit a right footed free kick taker more.
Do you have any ideas why the left foot conversion rate is better? Could it be that the angle for a left footed free kick makes it difficult to set up a wall? Are goalkeepers less used to positioning themselves against a left footed taker? Is there something going on with dominant hands? Or are left footed free kick takers just better? Please let me know your thoughts on Twitter and, once again, keep an eye out for my next post!
Until next time.
Sagar Jilka (@DrSagarJilka)
P.S. For those interested in the rest of the zones, here’s a table of left and right foot conversion rates across all the rectangles of the pitch: