Friday, 28 October 2016

The Addenbrooke to Zenga of Wolverhampton Wanderers.

It will be scant consolation to the recently dismissed Wolves manager, Walter Zenga, that managerial tenure has shown a decline over time and not only in the currently trigger happy East and West Midlands.

Wolves' first paid committee manager, Jack Addenbroke lasted an impressive 37 years, spanning the Victorian age and one World War.

But even if we begin at the start of the last old Golden Age with the appointment of Bill McGarry in the late 60's, time served by the boss has shown a downward trend.

McGarry's 398 games in charge during his first stint at the club was ended by relegation from the top tier after a May Monday night defeat at Molineux by Liverpool.

The maths were simple, a win for the hosts secured their First Division lives, while a win for the visitors won them the title. High drama that TV would die for, but in the 70's only radio put in an appearance to see a future Wolves captain lift the silverware for Liverpool.

Defeat sent Wolves on a footballing journey that only fleeting returned them to the top table.

Part of Wolves' Magical Mystery Tour post 1976. Blogger laughing because he's marking a goalkeeper!

At the dawn of footballing time, managers were lasting on average for around 150 matches, now it's down to about 50.

Success rate obviously plays a part in perceived managerial talent and Zenga's so so 47% success rate would typically entitle him to at least a season of honest toil, rather than the 17 matches he was actually granted.

His last game in charge perhaps sums up the knee jerk reactions prevalent today.

In keeping with 10 of the 14 league games contested by Wolves this term, their process created the better chances compared to their opponents.

In Zenga's final game in charge, typically a side would win slightly more times than they drew or lost were they have created 2.33 expected goals to 1.51 for their opponent

But not for the first time (7th April 1973), Leeds gained an undeserved 1-0 win.

Over Zenga's 14 league games, Wolves have a positive expected goals differential of 3.5 goals, rather than their actual goal difference of -1.

They've lost in three matches where they have been the superior expected goals team, drawing a further three in similar circumstances.

Their most likely current position based on process, without the sometimes perverse intervention of small sample sized randomness, is inside the Championship top ten rather than the current 18th spot that has played a part in Zenga's dismissal.

Even with their current lowly status, a more neutral division of shot outcomes over the remainder of the season places Wolves most likely finishing position at mid table........but in keeping with today's "enlightened" footballing age, the current small sample derived pecking order has already had a big say.

Spurious correlation. There is a medium to strong correlation between the first letter of a Wolves manager's surname and his tenure, and hence his Big Sam A it is!

Saturday, 15 October 2016

Once Upon a Time in the Midlands

Time was when an international break simply meant a manager spending an anxious couple of days waiting for injury reports to materialise and trying to keep the left behind players amused.

Now it seems to have become the prime firing time and just under half of the 2016/17 casualties from the four top English leagues have departed during the current hiatus.

Two of the higher profile dismissals have come across the east/west Midlands divide, with RdM being stood down for Steve Bruce at Villa and Steve McClaren reacquainting himself with Derby at the expense of Nigel Pearson.

Both sides are currently treading water just above the drop zone, respectively in 20th and 21st position and it's difficult not to speculate that current league position has played at least as big a part in the managerial changes as has a fear of drones.

Using drones may take spying on your employees to new heights, but it is equally questionable as to whether the league table ever gives a true representation of a team's true worth or if it is indeed the table of (in)justice.

Beware of Low Flying Drones.
Both Derby and Villa have a negative goal differential after 11 matches, but this isn't reflected in their respective expected goals figures for all the chances created in their games.

Derby's return of six goals is a poor one for a side that has created chances worth nearly twice that and the randomness that is inherent in short runs of matches has been less than kind to Villa, particularly in how it has bestowed goals in games and regularly turned three points into one late in their matches.

An extra couple of points this early in the season can easily turn anxious glances looking downwards into optimistic ones looking upwards to better things.

Both Derby and Villa are in the top half of the table when measured in terms of the underlying performance indicators that tend to persist amongst the ebb and flow of randomness that sometimes predominates, getting managers sacked or manager of the month awards, dependent upon whim.

Longer term, weighted expected goals performances smile even more on Derby, regular play off contenders, who are ranked around the top six in the current crop of Championship teams.

While Villa, despite giving the 2007/08 Derby vintage a run for their money with an abject defence of their Premier League life last season, still remain a top half Championship ranked side.

Final league projections at their most optimistic propel Villa to the fringes on playoff football, even without fully accounting for the potential impact of their new crop of expensive attacking talent, a relative luxury Bruce has never had before. And Derby fare even better, even with their miserly actual points return through 11 matches.

Fan reaction to the appointments is cautiously optimistic.

Derby fans in particular citing McClaren's ability to "improve a player", the unwelcome distraction of Newcastle potentially calling during his first stint and the example from the Stoke end of the A50 of returning managers taking their team to the top flight.

Should the fortunes of these two Midlands sides improve, this wishful impact of managerial change will appear to materialise, but it will be scant consolation to the replaced duo that the underlying figures were largely in place and the table may have become merely a tad less untrustworthy in their absence.

Saturday, 8 October 2016

Expected Goals Distribution in the Championship.

Everyone is familiar by now with the concept of expected goals.

The challenge is to present team figures in a way that demonstrates the granular nuances that are often lost by merely quoting totals or differentials.

It has also been accepted that how a sides expected goals is spread over their chances also impacts on the results they achieve. A side that takes lots of low quality shots compared to fewer, better quality opportunities is trading the chances of  an occasional headline grabbing goal glut for a more regular diet of lower scores.

The latter being preferable in a low scoring sport such as football.

A cumulative expected goals figure lacks granular data, while a full blown, chance by chance simulation reveals more, but is time consuming unless automated.

A decent halfway house is to plot the expected goals figures for each non penalty chance created and faced by a side over the season to date.

Scaled appropriately, the fatness of the left hand side of the plot shows the level of high quality chances a team has faced or made, while the length of the x axis illustrates chance volume.

Here's Newcastle, 11 games into their Championship season, out chancing their opponents with a long x axis and bulking up on good quality chances, while denying opponents the same luxury.

The highest quality non penalty chance they have conceded has a goal expectation of just over 0.4.

It's less rosy over 11 matches for fellow relegated side, Norwich who have allowed opponents a decent number of good quality chances and leaders Huddersfield currently profile more like a mid table team, such as Wolves.

At the bottom, Rotherham are currently being swamped by shot volume of fairly high quality, while offering little in return.