Bolton's Injury Woes.

As the 2011/12 Premiership prepares for it's final Sunday of action much is still left to be decided.Arsenal,Spurs and Newcastle are each eyeing third spot with varying degrees of optimism and the automatic admission to the Champions League that success will bring.Elsewhere matters at the top of the table will depend upon the result of QPR's visit to the Etihad Stadium and to a lesser degree on the outcome of events further north at The Stadium of Light,where Manchester United take on Sunderland.

Many have discounted the possibility of former Manchester United player and Manchester City manager,Mark Hughes' QPR taking anything from their match with City and so the relegation spotlight will once again fall on the Britannia Stadium and Stoke's match with 18th placed Bolton.Last year it was Wigan who made the trip down south to the Potteries requiring a draw or perhaps even a win to secure their safety and they duly delivered with a solitary single goal in the 78th minute.This time around,Bolton don't have the luxury of playing out a stalemate,they must take all three points and then hope that Manchester City win the title with 89 points courtesy of a win over QPR.

Little has separated Bolton from Stoke since the latter's return to the top flight in 2008/2009.The Potter's uneasy reintroduction to top flight football came during a 3-1 defeat at the Reebok on opening day in 2008 and the two sides finished within a place of each other come the end of the year.Stoke were three places above the Trotters the next year,but both teams ended the next year side by side again.Seasons do ebb and flow,but both teams ended each of the last three completed years comfortably above the drop zone.So what has changed this term that has seen Stoke perform largely to expectations,but Bolton enter the weekend as very short odds to drop into the Championship.

We saw here that the amount of playing days lost by a team due to injuries can at least in part explain that team's success rate over the course of the season.(Success rate is merely all a team's wins plus half of their draws divided by their total number of games).We further demonstrated that a team who experience a particularly low rate of injury attrition in one year and then a much higher rate in the subsequent season can experience a noticeable decline in that subsequent campaign.


There is no doubt that Bolton have been very unlucky with injuries this year.The near tragic,but ultimately uplifting story of Fabrice Muamba's remarkable recovery from a cardiac arrest during Bolton's cuptie with Spurs was a keynote event that touched all of world football.But from Chung-Yong Lee's season ending broken leg in pre season against Newport County to David Wheater's ACL knee injury sustained last week in their 2-2 draw at home to WBA,Bolton have had a steady stream of injured players at the Reebok.


On 38 occasions this term they have listed a first team squad player as injured and the combined playing time lost to these incidents is likely to be in excess of 1600 days.Figures can be hard to come by,so I've taken the date on which a player's injury was listed by Bolton and counted his lost playing time from that point to when he next makes a squad appearance.If we compare these figures to the 2010/11 seasons we can begin to appreciate the burden under which Owen Coyle's team have been asked to play.Only 23 injured players were listed during the previous year and playing days lost was around 500,a third of the total for 2011/12.

Therefore,under the definition I used in the previous post on how teams cope with their injury burden,Bolton had a light burden in 2010/11,but a heavy one in 2011/12.At the end of their 2010/11 campaign,Bolton had amassed 12 wins and 10 draws for a seasonal success rate of 0.45 and a relatively comfortable finishing position of 14th place and seven points clear of the drop zone.However,this position had been achieved with a relatively light injury burden and that was going to change dramatically in 2011/12.

If we refer to the table I publish in the previous injury related post we can see that 0.50 success rated teams with Bolton's two year injury profile on average see their success rate fall to 0.38 in year two.A 0.4 SR team fares even worse,falling to a 0.3 SR team.Bolton fall exactly half way between these two category of teams,having a SR in 2010/11 of 0.45.So everything else being equal we would have expected Bolton to have had a SR in the region of 0.34 in 2011/12 given their long injury list following on from a relatively benign one the previous year.A figure perilously below the average success rate for the final relegation spot in recent times of 0.35.

How Injuries Reduce a Team's Success Rate in Subsequent Seasons.

Success Rate in 2010/11.	Injury Burden in 2010/11.	Injury Burden in 2011/12.	Predicted Success Rate in 2011/12.
0.50	Light.	Heavy.	0.38
0.40	Light	Heavy.	0.30
Bolton in 2010/11. 0.45	Light.	Heavy.	0.34

Bolton currently have 10 wins and 5 draws from 37 games for a success rate of 0.34,exactly in line with their predicted SR given their record and injury burden in 2010/11 and their injury burden in 2011/12,had we known it in advance.If they beat Stoke on Sunday they will lift it towards 0.36,but that's still close to the SR rate gained by the best of the relegated trio,so they are fortunate that QPR are involved in a meaningful final contest.

It is dangerous to assign one factor too much significance in a side's apparent decline from one season to the next as often teams can under or over perform against their bi annual injury profile because of a multitude of different and competing factors,but Bolton have certainly faced adversity this term.Managers are often prone to exaggeration,but few will dispute Owen Coyle's view that Bolton have had "a freak season in terms of injuries".