Friday, 10 May 2013

Strikers Are Better Finishers Than Defenders.

Shooting ability is one of the most coveted of footballing skills and the prices paid for the likes of van Persie and the speculative sums quoted in relation to any potential sale of Gareth Bale confirm this. It has become increasingly possible to quantify shooting talent, first by collecting large amounts of goal attempts and assuming that equality and quality of chances are evened out over such large sets. We can further sub divide these numbers into set piece, open play or headed attempts and finally by using x, y coordinates we can try to ensure that players who consistently shoot from advantages ranges don't see their numbers artificially inflated. Although we shouldn't overlook the fact that the ability to continually shoot from closer range is probably a talent as well.

Therefore, x and y data analysis offers a promising way to begin to evaluate the relative merits of individual players, although the influence of short term random fluctuation should be appreciated and the absence of additional inputs, such as the position of opponents would also prove helpful.

An individual player who scores more frequently than expected given the position from which he shots can be considered to have had a successful season, although consistent over performance over a larger period would be needed to confirm a repeatable excellence. However, we can take a more general look at a larger data set by dividing players simply by position to try to confirm that some groups of players are more proficient shooters than others.

Strikers are primarily purchased to score goals, whereas defenders require different talents and so it is reasonable to assume that the former, overall have better shooting capabilities than the latter. If we can confirm a difference in shooting ability between different positional groups, it is also likely that a spread of talent within these separate groups also exists.

 Average Likelihood Of Players Scoring With A Central Shot From 14 Yards.

Player Position. Chance Of Scoring With Shot From 14 Yards. Chance Of Shot Being On Target from 14 Yards.
Defender. 15% 31%
Midfielder. 22% 44%
Striker. 25% 47%

Average Likelihood Of Players Scoring With A Central Shot From 25 Yards.

Player Position. Chance Of Scoring With Shot From 25 Yards. Chance Of Shot Being On Target from 25 Yards.
Defender. 5% 21%
Midfielder. 8% 31%
Striker. 10% 34%

The conversion rates above are derived from regressing x,y coordinated shooting attempts across most of the teams that have recently played Premiership football. All headers have been excluded along with obviously higher value opportunities, such as penalties. By including a term to represent the designated playing position of all players, I have calculated the drop off in observed conversion rates as we go from strikers, through midfielders to defenders at varying distances from the goal and maintaining a central position. Strikers, in general are almost twice as effective when shooting from just inside the box than are defenders and this repeats at much longer distances.

The divide in shooting talent appears clear between groups of players, although defenders may be shooting in situations immediately following a corner, where the defence is more concentrated and as we begin to add terms for defensive pressure to such models, these effects will hopefully become better defined. Conversely, some defenders may not even get the opportunity to impress or otherwise with their shooting prowess. Defenders account for almost 40% of playing time, but contribute just 15% of shots, compared to a near reversal of numbers for strikers. Therefore some of the poorest shooting defenders may be almost completely absent from the sample.

Heading ability is one area where defenders may be expected to close the scoring gap between those more usually charged with the task of scoring goals. However, again strikers and midfielders appear to be both more efficient and more accurate with their efforts than the average defender. Although again defenders who do venture forward are more likely to do so at set pieces, where they are bound to attract attention from the best markers.

Average Likelihood Of Players Scoring With A Central Header From 7 Yards.

Player Position. Chance Of Scoring With A Header From 7 Yards. Chance Of Header Being On Target from 7 Yards.
Defender. 20% 28%
Striker/Midfielder. 27% 38%

Methods that confirm widely held beliefs are as important as ones that challenge the status quo and that the best finishers tend to be strikers and midfielders shouldn't surprise given the premium that such skills attract in the market. A lethal finisher, especially from open play is much more valuable when playing in a position where he can showcase his rare talent and while the transition from defender to striker is almost certainly a leap too far, the conversion rates of defenders and midfielders is much closer.

Midfielders account for just over 40% of total playing time and account for nearly 50% of a side's shots. So often from a purely shot conversion viewpoint it is simply access to opportunity that distinguishes the number of goals scored by a similarly talented defender compared to a midfielder of near identical shooting abilities. Bale's transition from fullback to goal scoring midfielder may have been partly written in his early stats.


  1. Interesting read, I am a bit suprised that Striker/Midfielder are still better at Heading than Defender. Maybe there are just some Outlier in the defenders group just like Rio Ferdinand etc. who are just world class.

    P.S: Where do you got the data from?

  2. Hi Mindgamesdotme,

    I think the heading stats are almost certainly skewed by the number of opportunities that arise for defenders from set plays and corners, which tend to be more heavily defended.

    The data is a mixture of self collected from stat zone 442 ipad app and some kindly provided by Opta.