Tuesday, 1 November 2011

Poor Results Don't Indicate a Decline in Fortune.

Over the course of the EPL season so far Arsenal,Chelsea,Liverpool and Manchester United have each suffered heavy defeats.Arsenal conceded 8 goals at Old Trafford,although they weren't helped by a red card,a similarly player deficient United conceded 6 at home to neighbours City,9 man Liverpool shipped 4 against Spurs and then Arsenal bought everything full circle by scoring 5 in defeating the last of the original Big Four at Stamford Bridge.

Dire warnings of impending doom has variously followed each drubbing,but are conclusions based on one isolated result or even a more prolonged series of under performing games often extreme and inaccurate ?After all Arsenal,for one appear to have recovered fairly quickly from their fall from pre eminence if their 5-3 win at Chelsea is anything to go by......or perhaps I'm just placing too much importance on last Saturday's result.

Heavy defeats seldom signal a sudden precipitous decline in fortune for teams outside the Big Four,so it's likely that successful,well resourced teams such as Man United would be just as able to overcome an embarrassing,but isolated poor result and be able to carry on much as normal.The margin of defeat suffered by the original Big Four is certainly shocking and headline grabbing,but even these must be placed in their proper context.Scoring is certainly higher in the EPL at the moment,leading to such luminaries as Lee Dixon to concluded that officialdom is trying to banish virtually any type of contact from the game,making defending more difficult and ultimately scoring easier.

Secondly,the damage this season has been inflicted on the top teams by one of their own or in Liverpool's case by a team with aspirations to belong amongst the best.

Lastly,red cards contributed to three of the four defeats.United conceded 5 of the 6 goals scored by City after they had had Evans dismissed,including 3 after the 89th minute,Arsenal allowed 2 more goals after Jenkinson's dismissal and 3 of the 4 scored by Tottenham came against 9 Liverpool players.Therefore,if we wish to gague the performance of the Big Four after a heavy defeat we would probably have to eliminate these three games from the sample.That leaves us with precious few occasions where the top teams have been heavily defeated,so an alternative approach is needed.

Pundits are fond of describing the kinds of run a team is on."Undefeated in the last five games" implying invincibility,while "without a win in five" is the usual pre amble before managerial change is discussed.Therefore to bulk up the sample size I looked back over the seasons to find any run of five consecutive EPL games where one of the original Big Four had failed to record at least one win.As you would expect these are unusual occurrences for the Big four,the chances that they would not win at least a game in a run of five matches on average exceeds 100/1,but they do happen around once every 4 seasons per team.

I used the average success rate for the teams during their poor to measure their form over the 5 games.Success rate is calculated by counting a win as 1.0 success points and a draw as a shared 0.5 a point  for each team.I then calculated the average success rate per game for the Big 4 side for 20 games prior to the start of the run and for 20 games subsequent to the poor run.Obviously,this meant that some of the games post or pre the "slump" were played in different seasons,however I have consistently found that more data even at the expense of recency is a better indicator of a team's future performance than if you restrict observation just to the single season.

Success Rate of Big 4 Prior to Poor Run.
Success Rate During Poor Run.
Success Rate of Big 4 After Poor
0.76 0.40 0.76

Prior to the teams experiencing a 5 game non winning spree the Big 4 were averaging a success rate of 0.76.During the 5 game slump this fell by almost half to 0.4,but after the apparent slump the success rate returned to the levels of the previous 20 matches.It would appear that a run of unusually bad results can be expected from any team,not just the top ones.It would be inconceivable if this wasn't the case,although you would have to trawl a lot of data to find some of the more unusual cases,but they are almost certainly not an indication of a permanent downturn.If 5 under performing results in a row don't indicate immediate ruin for a team,it would seem premature to also herald a team's decline after one thumping.Team quality changes very slowly over time unless there are clear and obvious reasons why a team has suddenly improved or declined.

The Manager of the Month is often viewed as a curse because poorer results often materialise,but if short term bad scorelines occur naturally with little change in a team's underlying skill levels,the same is likely to be true for unusually good results.So when a mid table manager is rewarded for a good month of results,don't be surprised when his team then slumps (aka returns to it's more usual level of performance).......expect it.

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