Thursday, 12 January 2012

Optimising Your Transfer Window Purchases.

Crack open the Bovril and heat up the Wright's pie because the EPL has reached the half way stage and it's time for the transfer window to provide a last chance for teams to cement that better than expected start and transform it into tangible rewards come May.Or more stressfully,it's a final opportunity to get enough able and willing bodies on board to fight off the dreaded specter of relegation and a reluctant starring role on BBC's soon to be axed late night Championship Show.

Artificial and contrived it may be,there's no doubting the January window is a dramatic and compelling addition to the football calendar.As a footballing antidote to the post Christmas blues,it's second to none,be you a fan with opinions to share or a slightly unsettled player with a fleet of high performance cars in urgent need of chrome plating.

So what's the best way to ensure that your January sales purchases are providing the biggest potential boost to your current fortunes by addressing the weakest part of your squad instead of merely reinforcing an already well performing aspect of team performance.The first stage of the process should be to be realistic about your goals.Teams at the foot of the table are obviously there because they lack quality throughout the side.It's a futile exercise to compare the current state of teams like Bolton,Wigan and Blackburn to even the league average benchmarks or you'd simply conclude that they each needed at least half a dozen new improved players.And that isn't going to happen because the money isn't available.If it were,such teams would struggle to attract quality players anyway.And if they somehow did attract them,such a large number of new signings would need time to gel and possibly adapt to Premiership which time we'd have reached April Fools Day and continuing under performance would likely be assured.

What's needed is a way to compare the attacking and defensive qualities of teams while also accounting for their current overall league position.As any young aspiring athlete knows,improving your weaknesses is often a quicker and more efficient way to advance a team than trying to improve further on your strengths.We therefore now need a team stat that can be broken down into defensive and attacking components,but as we are just half way through the season,it also has to correlate well with itself.We can then use the information derived from this to decide where the rebuilding is going to be targeted.

We saw here how well team statistics auto correlate from the first half of the season to the second and it's clear that a shot based approach may be the best.However,we also need to know how strongly the statistics correlate with team success rate,because ultimately that is what every team,not just the struggling ones are striving to improve.Shots are only moderately correlated to success rate and that correlation doesn't improve if we add a shot efficiency component to the analysis.More importantly,we've seen here that shot efficiency is very context dependent even over entire seasons.Trailing teams are less efficient than teams who are playing with a lead.Scoring go ahead goals is partly luck driven and this shows up more in limited sample sizes.Thus,it should come as no surprise that shot team efficiencies show virtually no correlation for EPL teams as a whole when measured over half seasons.

We've seen here that goal difference is correlated far stronger to success rate than any other commonly recorded team statistic,it's also moderately correlated with itself,therefore a combination of reasonably strong auto correlation and very strong success rate correlation makes goal difference a much better choice to define a team's August to December record.

As a final strand in our massive game of Connect Four,we have broken down the various components that go towards a team's overall goal difference in this post. Armed with this analysis we can use a side's current goal difference,compare that side's attacking and defensive performances with the average performances expected from a side having a similar goal difference and see were the team's rotten under belly really lies.

The Historical Scoring Contribution to a Side's Goal Difference in the EPL 1999-2010.

The Historical Defensive Contribution to a Side's Goal Difference in the EPL 1999-2010.

I don't want this post to become a tedious number crunching fest,so after a pared down illustrative example,I'll merely list each team's strength,weakness or for fairly balanced sides neither.Blackburn probably aren't the best example to use because most people would question their board's commitment or competence,but Rovers do have a readily discernible talent divide.Their current goal difference is -0.7 and their position of bottom,but just three points from 16th reflect this.To achieve this goal difference they've scored 1.45 goals per game and conceded 2.15 goals/game.If we now look at each of the graphs above we can see that historically a team with that goal difference would have scored around a goal a game and allowed their opponents to score around a average of 1.7 goals each game.Therefore,we can conclude that Rovers are an above average attacking side for their current position (They've put 4 past both Arsenal and Swansea and 3 past United at Old Trafford.),but a below average defence.

Realistically they should be aiming to become an average defensive side in their sphere,whilst trying to maintain their attacking prowess,thereby improving their goal difference and moving up the EPL ladder by a couple of rungs.It's likely that their attacking numbers will regress toward the mean for poor EPL sides after January,but they should still be above the norm for strugglers.Likewise their defence is likely to improve slightly because of random fluctuations,but genuine improvement from such a low level should be achievable through drafting in better loan or permanent signings and better coaching.Many coaches are of the opinion that poor defences can be made markedly better through easily implemented organisational routines,but no amount of coaching can teach a striker the Cruyff turn.Another reason why strikers attract a premium,they tend to be born rather than manufactured.

Whether the Blackburn board are willing or able to play ball is another matter.They do at least have a saleable defensive asset in Samba who could be used to finance a couple of purchases that may decrease the talent of the parts,but increase the effectiveness of the whole.

If we repeat the process for every EPL team we can highlight the weaknesses sides are showing given their current league position and goal difference by comparing them to historical precedences.To make the following table more easily readable I've simply colour coded the findings.Green means good to go,red means in need of attention and amber means teams are fairly close to being an historically well balanced attack and defence.Current injury concerns aren't factored into the analysis,for example Everton only have two fit central defenders,two less than Stoke habitually include in their starting line up.So following Jagielka's long term injury they will have to ignore their attacking needs and get in defensive reinforcements instead.

Where Teams Should be Making their January Purchases. 

TEAM. State of
the Attack.
State of
the Defence.
Sunderland. ATTACK. DEFENCE.

Rather counter intuitively,it is the team without a gaping hole in their team who will find it most difficult to actually move far from their current position.They have been playing at a level on both sides of the ball that is largely consistent with their current position.They will struggle to attract signings that are any better than the type of players they already have on board,so any purchases are more likely to prove squad depth than any great leap forward.Wigan for example are playing relegation football,but with no obvious route to improvement,whereas both relegation rivals,Bolton and Blackburn have an open sore defensively and a means to bring in players at the cost of one outstanding member of a grossly under performing unit.They at least have a survival strategy.On a level playing field you would worry for QPR and Wigan.

Will this season see Wigan's lack of quality finally catch them out?
(Spot the brave Wigan fan in the Stoke end!)
To conclude and provide an embarrassing recap come May,we can assume that each team does manage to haul their under performing unit up to league average levels for their current position and maintain their strengths,we can armed with their likely new and improved goal difference simulate the remaining 18 games of the season,total this to their current points total and predict a final table.

Predicted Final EPL Table 2011/12.

TEAM. Predicted
Man City 97
Man Utd. 89
Tottenham. 81
Chelsea. 73
Arsenal. 69
Liverpool. 65
Newcastle. 61
Sunderland. 51
Norwich. 51
Stoke. 49
Everton. 49
Swansea. 48
Aston Villa. 46
Fulham. 46
West Brom. 43
Blackburn. 36
Wolves. 35
Bolton. 34
QPR. 33
Wigan. 27

No huge changes in positions,the table is usually very well established by mid term.But there's certainly  opportunities for teams at the bottom who are prepared to target their spending.The now customary log jam at the bottom looks likely to re occur and there's welcome slippage at the top with the possibility that some previously permanent members of the Big Four making way for a couple of fresher faces.

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