Saturday, 15 June 2013

Counter Culture.

One of the biggest problems associated with analyzing footballing performance is the overall lack of available data, both in quantity and quality. Goals are of course universal, but more granular data such as shots on target and conversion rates have only been available for recent seasons and if we move up a level to include x, y data, both collection and availability problems become even more severe.

The level of understanding that comes with increased detail in the data can be demonstrated by the usual case of Stoke City. Low frequency, but high conversion rates for their chances created over their initial tenure in the Premiership, would seem to be a perilous, luck driven and unsustainable way of staying in the top flight. But by looking at the positions close to the goal from where they converted a large proportion of their chances, especially in the early seasons, the Potters' continued survival just the right side of the 40 point barrier becomes slightly easier to rationalize. Without knowing that Stoke scored many of their goals in or around the six yard box, they would appear as an extremely lucky outlier or a team with outstanding finishers (if indeed such a player commonly exists).

However, paying too much heed to the unusual can obscure the perfectly acceptable work that can be done with the more basic data. Goals scored on the counter attack are assumed to fall into a similar niche category as the type of set piece strikes that have kept Stoke afloat over recent Premiership seasons. Teams of quality are widely perceived to cherish possession, leaving the lesser sides to contest their own glass ceiling, where goals are scrimped from less conventional means.

Goals from Counter Attacks for EPL Teams with 100 or more Open Play Goals. 2009-13.

Team. Total Goals from Open Play. Goals from Counter Attacks. % of Open Play Goals from Counters.
Manchester City. 196 24 12.2
Arsenal. 230 28 12.2
Aston Villa. 124 15 12.1
WBA. 102 11 10.8
Tottenham. 188 20 10.6
Wigan. 106 11 10.4
Chelsea. 208 17 8.2
Everton. 140 11 7.9
Liverpool. 160 11 6.8
Newcastle United. 104 7 6.7
Manchester United. 230 15 6.5
Fulham. 116 7 6.0

Above I've outlined the percentage of open play goals that teams score on the counter attack over the previous four completed seasons. Using this basic analysis we can try to draw some conclusions that may be developed further. Firstly, there appears to be little correlation to finishing position. High achieving sides, such as Manchester City and Arsenal score a league high proportion of their open play goals from counter attacks, yet similarly talented Manchester United recorded a near league low percentage.

The spread of percentages ranging from a high of 12% to a low of 6% would imply that there is a clear difference in the ability of Premiership sides to convert on the counter. However, the disparity is unlikely to be as large as these raw numbers imply. Sample sizes are relatively small and a heavily regressed figure ranging from over 50% regression towards the mean for the larger samples to nearly 80% for the smaller ones, would seem in order. A more predictive figure would likely be highs of around 10% of total open play goals and a low of just over 8%.

Goals scored on the counter are by their very nature partly opportunistic, so match situation will likely play a considerable role in the regularity of their appearances. However, there does appear to be a cautious connection between squad age and the ability to create rapid fire counter attack scores. Fulham, currently have the Premiership's oldest outfield squad and perhaps significantly, they are the least reliant on counter attack scores from open play.

If we move from the basic counting stats for counter attack scores, we can begin to put more flesh onto the characteristics of such goals and also add weight or otherwise to the tentative conclusion from the basic data.

By cross referencing the category of goals scored to the x,y data we can try to see if the quality of chances created on the counter, when defensive set ups may be both less organised and less well manned, differ from "normal" goals scored during open play.

In the data set I have around 5% of open play chances are created on the counter. However, counter attack goals accounted for 10% of the goals scored, so the conversion rates of counter attacking chances appear greater than those for normal non set play opportunities. Conversion rates were 15% for the former and around half that for the latter.

If we use the x,y shot data matched to actual outcome, the ultimate origin of the chance does appear to be significant, with  opportunities created by way of counter attacks appearing statistically significantly easier to convert. To illustrate this, consider a penalty kick where the conversion rates in the EPL approaches 80%. If a shot is taken from the same spot from a counter attack, in my sample the expected conversion rate drops to just over 30% and if we project the expected success rate from none counter attacking open play scoring opportunities, the rate drops again to below 20% .

A quick Swindon counter catches out the Stoke defence.
So how you create a chance would appear to be a major factor in converting them successfully. Equally stark, at least in my sample, is the mode of execution. Around 10% of normal open play chances are executed with the head, yet chances taken from counter attacks were virtually exclusively shots with the feet. Similarly, defenders were rarely on the end of a counter, but they were on the end of nearly 10% of all other chances created from open play.

Small sample sizes often lead to extremes of results, but hopefully the overall trend remains and the size of the disparity between individual results can be tempered by regressing aggressively towards the mean. Counter attack goals we may tentatively conclude are slightly more likely to originate from young and presumably quicker players throughout the outfield team, they present clearer cut chances than other open play scoring opportunities from the same shot location and they seem to be more controlled moves because chances inevitably ended with a shot rather than a header.

10% of open play goals would seem to be the natural upper limit for sides to aspire to on the counter. So despite a high expected conversion rate, it would appear that attempting to build a side to exploit opponents on the break is the poor relation in niche tactical approaches, such as one based around set pieces, where the opportunities and therefore, goals are more numerous.

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