Monday, 21 April 2014

Which Summer Premiership Buys Bloomed in the Spring?

The summer and winter transfer windows afford Premiership teams their only chance to substantially strengthen their squads with quality players. Considered judgement is made and opinions are backed with hard cash to acquire players who will hopefully form a nucleus for a successful squad for the foreseeable future.

In a sport with notoriously short term agendas, it is perhaps unfair to attempt to assess the winners and losers from last summers transfer spending spree, but in the spirit of the current awards season, we'll give it  go.

Transfers, of course involve defensive players, mid fielders and attackers and in view of the lack of really objective measures at the moment for the defensive side of the ball, a rating system based on player statistics would prove problematical. Therefore, we perhaps should fall back onto a much more valuable resource in evaluating a successful transfer, namely the experienced opinion the man at the top, the manager.

Playing time can be used as a good proxy for talent in assessing such things as ageing characteristics. Premiership teams have reasonably deep squads and a player who is appearing regularly is likely to be one of the top performers within his team.

However, playing time alone, requires context as well if we are looking at the success or otherwise of a transfer. The playing time achieved by a player is likely to be correlated to his transfer fee. Better players cost more and overall should perform to a higher level than those who cost less.

Age will also be a factor. Most players who attract a fee are generally aged in their twenties, but a player just out of his teens may be bought as much as a future investment than as a potential ever present in the current season of his purchase. By contrast, a player in his mid twenties would be more likely to be purchased as an immediate and useful full time starting player, before age related injury and depreciation sets in.

The third major consideration revolves around the talent levels of the side making the transfer. A £5,000,000 purchase for a promoted side would be a considerable investment and the expectation would be that the player would command a regular starting spot and considerable projected playing time. Whereas, a similarly priced player would be much less likely to make a similar impact at a top side, where talent levels would be higher. He may even initially be purchased as loan fodder with which to inconvenience the ambitions of his parent club's rivals.

These parameters can be used to create a baseline for playing time for particular transfer profiles.

For example, if a struggling Premiership side, had paid around £8 million for 24 year old in the summer transfer window, the average expected playing time, based on historical precedent, for your purchase would be around 60% of the time available in his first season. A more experienced player, nearing 30 would be expected to be on the field for the same side nearly 70% of the time.

Compare that to under 40% of playing time if a similar transfer had been to a top four side instead.

 The Ten Best Transfers Made in the Summer Window, 2013/14.

Player. Club. Cost.
(£ millions)
Age. Proportion Of  Playing Time.%
A Elmohamady. Hull. 2 26 97
S Caulker. Cardiff. 8 22 100
E Pieters. Stoke. 3 25 88
C Davies. Hull. 2.25 29 97
J McCarthy. Everton. 13 23 81
L Bacuna. Aston Villa. 3 22 79
M Olsson. Norwich. 2.5 25 85
T Huddlestone. Hull. 5.25 27 93
D Lovren. Southampton. 10 24 80
N Redmond. Norwich. 3.2 20 62

Above, I've listed the summer purchases whom have bettered their projected playing time by the greatest amount and thus may be considered to have exceeded the hopes and expectations placed in them by their new club.

Hull's Amhed Elmohamady tops the list, although he and Hull had the advantage of a season long loan to bed in at the KC Stadium during their Championship season of 2012/13. Therefore, England prospect, Steven Caulker should probably take the accolade. His transfer fee was four times that of Elmohamady, but he is considerably less experienced at 22 and under this simple metric, his ever present status at an inferior team, Cardiff, only just failed to overhaul the Hull player for outright leader.

A couple of modestly priced, relatively mature (in age anyway) players follow closely, Erik Pieters at Stoke and Curtis Davis, again continuing the apparently impressive team building done by Hull in the summer window.

Steven Caulker prepares to say "Pob Hwyl" to Spurs and "Helo" to Cardiff.
Of the higher priced purchases in the top 10, McCarthy at Everton and Lovren at Southampton stand out and mega pound, but relatively successful purchases bubbling just below, include Fernandinho at Manchester City, Eriksen and Paulinho at Spurs and Bony at Swansea.

I've omitted keepers, purely because they tend to have few pretenders to their place in the starting lineup, but Mignolet, Mannone and McGregor (at Hull) top the list of newly acquired stoppers.

Inevitably there is a bottom ten, but a metric based partly on appearance minutes is obviously susceptible to injuries.

Everton's Kone prove the least successful summer purchase, a £6 million pound, 30 year old player should be expected to play nearly half of the available minutes at a top 6 side in his first season. Although injuries are partly out of the control of a team or player, his history and age perhaps suggested the price paid was too high for the potential risk. He has been absent through injury since mid October.

Cardiff's John Brayford was a non injured failure from Derby. The fee was relatively modest, £1.5 million, but as a 26 year old he would  have expected to feature in around 45% of playing minutes. Instead he failed to play a single minute and is now out on loan. Cardiff suffered a similar disappointment with the transfer of Peter Odemwingie, a more costly and older investment who failed to impress enough to command a regular starting place and his swap move to Stoke was bi-laterally agreed in the winter window.

Palace, Sunderland, and Villa spent moderately, but with a fair few underperforming individual returns at this end of the ledger and big priced summer disappointments, some partly injury mitigated, include Fellaini at United, Osvaldo at Southampton, Jovetic at Manchester City and Lamela at Spurs.

Friday, 18 April 2014

Luck Can Make An Average Team Appear Special.

It is very easy to be drawn to extreme performances, either good or bad when looking at the analytical side of football. Exceptional performance stands out, is always highlighted in the media and talked about by the fans. It's difficult not to get carried along.

Liverpool's title charge and the consummate ease by which Crystal Palace cruised to 40 points, of course is partly down to the expertise of their respective managers, fans and players, but it is also likely that random fortune also pushed their sides higher, as well.

The temptation, though is to look for the cause to the effect and ascribe 100% of the former to the latter. But the praise is rarely fully deserved and the criticism is often unduly harsh when expected success fails to arrive promptly.

One way to avoid the almost irresistible rush to narrative, is to start with a singularly anonymous team, one that, for a season,at least is steeped in mediocrity. 52 points with a barely positive goal difference has been the average seasonal performance of a Premiership team over the last decade and the Spurs team of 2004/05 exceeded no one's expectations by recording this benchmark.

The side Martin Jol inherited mid term from Jacques Santini finished 19 points clear of the drop, 43 points from the summit, reached the 6th round of the FA Cup before losing to Newcastle and the 5th stage of the league cup before bowing out to Liverpool, despite taking the first kick in the penalty shootout. They failed to defeat any of the then Big 3 of Arsenal, Chelsea or Manchester United and their 52 points were exactly in line with expectations from their pre-match odds over the 38 games.

So the 52 points gained by Spurs in 2004/05 probably reflected the most likely outcome for a team of their ability playing in that season's Premiership. It is a comforting occasion when theory and reality combine to give the illusion of control without the appearance of outlying products of talent and a lop sided portion of random chance.

The range of possible outcomes from a group of games is most easily demonstrated by simulating seasonal outcomes using strength of schedule adjusted match odds. The usual method projects the range of league points that might be posted by a side of say Spurs talent once the vagaries of random chance are given full rein by continual repetition. However, it is a simple process to break down a team's match probabilities into individual slices that quantify the chances of winning or losing by a particular margin.

So alongside the usual range of points projections, we can add another commonly used statistic, namely goal difference.

How Likely Winning or Losing Margin Varies with the Chance of Winning the Game Outright.

Chance of Winning the Game. 65% 46%
Winning By a Margin of 1 25% 24%
Winning By a Margin of 2 20% 14%
Winning By a Margin of 3 12% 6%
Winning By a Margin of 4 5% 2%
Losing By a Margin of 1 10% 17%
Losing By a Margin of 2 3% 7%
Losing By a Margin of 3 0.8% 2%
Losing By a Margin of 4 0.1% 0.5%

Spurs' cumulative points expectation from the individual match odds for all 38 league games in 2004/05 was that they would get 52 points and typically that would result in a goal difference of small, single figures.

However, just as it is possible, but highly unlikely that an average side could either win or lose all 38 matches, a single iteration may see a side of Spurs' 2004/05 talent deviate from their expected average and in doing so produce atypically higher or lower goal differences.

The most likely goal difference is indeed centred around zero, but there is also a reasonable chance that our league average side might record multiple years when their goal difference drops well into negative double digits or rises to similar positive heights.

If we take the 2004/05 season as a benchmark, Spurs' range of possible goal differences only begins to peter out as they record values matched by Manchester United, who finished 3rd at one extreme and Norwich who were relegated at the other.

Even with thousands of repetitions, sample sizes start to fall as we look at the spread of actual points recorded by the same goal difference. But the spread of points gained with the same goal difference, in this case -2, is similarly wide, if slightly less well defined, falling into the low 40's and as high as the early 60's. If we again look at the 2004/05 season, Everton recorded a goal difference of -1, but won 61 points.

If average Spurs, mk 200405 can produce an impressive array of goal differences from the same talent base and an equally diverse range of league points from seasons with identical goal differences, the random walk should also be apparent within individual seasons.

Below are two final plots that trace individual seasons taken from just a couple of dozen simulations using our generic, average team and patterns and trends, that could be easily mistaken for real changes within the team are readily apparent. Even though they have been generated from the same game odds, used in an identical order.

The first graph could easily be depicted as a promising start that stalled after around a dozen matches and then got progressively worse as the side stumbled over the survival finishing line, before the season ends on a low point and four consecutive losses.

While the second plot, again drawn from the same match probabilities, show an almost polar opposite. A poor start is gradually arrested and followed by an impressive second half of the season, containing a 12 game winning streak and likely  UEFA Champions League qualification, probably in the first qualifying round.

Two very different outcomes to essentially the same talent laden season, made possible by the random distribution of rewards in a short 38 game period.

Fortunately, even when we try to chose a mundane, everyday side to illustrate how the same talent base can produce very different results, an event often intervenes to proved a potential narrative where none really exists.

Santini left to be replaced by his assistant, Jol after 12 matches. Jol's first match in charge was a 4-5 loss at home to rivals, Arsenal. And each of these graphs provides convenient inflexion points at or around 12 matches and it would be incredibly hard to resist attaching the cause of a managerial departure to the effects seen in either plot.

Even if we knew that both were merely produced as one possible reality out of many with the help of a spreadsheet.

Thursday, 17 April 2014

The Race For 1st and 4th.

A quick piece of housekeeping to follow up the relegation post after the weekend games.

Liverpool's win over Manchester City failed to settle the title race, but it did tilt the odds strongly in favour of the victors. The Reds and particularly Chelsea, then watched on as Sunderland came within minutes of taking all three points from City on Wednesday night, before gratefully settling for a draw.

The title now lies in the hands of Liverpool and Chelsea, win out and that side will be crowned champions by virtue of their head to head meeting at Anfield at the end of April.

Title Odds as of 17 April 2014. 

Team. Liverpool. Chelsea. Manchester City.
Title Likelihood. 65% 22.5% 12.5%

Chelsea will be the outsiders of three at Anfield, behind Liverpool and the draw, hence the large preference for Liverpool to take the title. However, match odds of around 47% for a Liverpool victory refer to longterm expectation, rather than a single iteration, so chance and luck will quite likely play a part as they did at Anfield on Sunday.

Goal difference has largely become cast in the title chase. There's around a 5% chance that Chelsea and Liverpool will end the season level on points, but virtually all of these ties would be settled in Liverpool's favour. A 5 goal margin of victory in the head to head would be needed to wipe out Liverpool's current advantage in one swoop, (somewhere in the order of 1,000/1), but even then the sides would also need to finish level, most likely on 84 points. Nine goals is too big a gap to bridge in just four games.

City trail both Chelsea and Liverpool, but have a superior goal difference. If they catch one or both (a triple tie is about a 0.5% chance), they almost certainly maintain or increase their current advantage.

The title is now Liverpool's to lose.

Goal difference is one straw that the blue half of Merseyside are currently clutching after Pulisball found its unlikely vindaloo factor by scoring one more than Everton as Crystal Palace reached 40 points in a 5 goal thriller. Should Liverpool falter, the clamour to crown Tony Pulis manager of the season may prove irresistible and the irony won't be lost in the Potteries, if clever defensive spoiling and set piece efficiency suddenly becomes fashionable five years after its inception.

Roberto Martinez is correct in stating that even Everton's current slender three goal difference superiority could prove decisive in the battle for 4th, although only in a minority outcome. If the teams are tied at the end of the season, Everton win nearly 90% of those occasions by virtue of goal difference. Unfortunately, ties are only likely to occur less than 5% of the time and overall Arsenal took a huge step towards securing UCL football on the back of a favour from their favourite pantomime villain and the honesty in the penalty area of West Ham's Matt Jarvis.

4th Place Odds as of 17th April 2014.

Team. Arsenal. Everton.
Likelihood of 4th. 85% 13%

As over at StatsBomb points out, Pulis is now cast in the role of Kingmaker. Having fatally wounded Everton and greatly inconvenienced Chelsea, he faces both Liverpool and Manchester City, against whom his record with a similarly hard working Stoke side was excellent in matches away from their home comforts.

During Pulis' reign at the Britannia Stadium, a Stoke side that was assured Premiership football next season looked and played very much like any other Stoke side and for all that he departed Stoke on relatively good terms, it must appeal if he could end the season with Palace positioned above Stoke.