Data Rant: in search of goals

May 16, 2015 Tags: , Data No comments
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Manchester United has qualified for next season’s Champions League and a good result against Arsenal – together with any further slip-on on the London side’s part – may even see the Reds sneak directly into Europe’s premier club competition. United must finish third to avoid a Champions League play-off against potentially difficult opposition next August.

United has made an unusually early move in the transfer market this summer with the purchase of Memphis Depay. It is one that makes much sense and could be the first of many arrivals at Old Trafford says  Ed Woodward.  United’s vice chairman claims that the “squad will be absolutely deep enough and ready to challenge on all fronts.”

Taking care of a defence that has not always been solid this season is priority, but more or less straightforward. The situation further up-field, however, is complicated. United’s engine room needs work, but so does the strike force  where Wayne Rooney, Robin Van Persie and Falcao have failed to convince over the past year.

As ever Rooney complicates matters as the armband dictates the Englishman’s selection. His best position is number nine so bringing in a top midfielder may be the easiest move politically for Van Gaal this summer. The question of whether United actually needs a top midfielder is still relevant though.

Depay, as callow as he is, will take Ashley Young’s place on the left. The Dutchman’s superior quality on the ball will then remove the need for Maroune Fellaini to hold the ball on the left side of midfield. The consequence is that Angel di Maria can then be deployed in the role that he has played for Benfica and Real Madrid, in a central attacking midfield position, leaving Juan Mata and Adnan Januzaj to fight it out for the right-wing berth.

Mata has been effective as a “false winger” in recent weeks, while Januzaj is more likely to get a look-in with Depay, a classic inside forward, operating on the left. For a left-footed player, the Belgian is comfortable attacking the byline from either flank. Van Gaal will look to compensate for the width Ashley Young has offered this season, while Depay will add more goals and assists than the Englishman.

Still, the Champions League will place further strain upon an injury-prone squad. Acquiring a new striker will introduce a healthy degree of competition, especially for Rooney, while a world-class midfielder will strengthen an area key to Van Gaal’s philosophy.

Up front evolution is needed – goals win points and points bring trophies – and United has been lacking goals this season. It is an observation that means Van Gaal will evaluate his candidates on the basis of goalscoring prowess – an area in which Memphis offers much with the Dutchman on 29 goals for the season.

However, goals come in many flavours. A goal that has been ‘created’ is matched by an assist. So the number of total goals minus number of assists are ‘gratuitous goals’ – set pieces and goals gifted by opposition.

Intuitively, a team should concentrate all its energy on ‘creating’ goals rather than waiting for the opposition’s mistakes. The higher the assists divided by goals the better the ratio of created goals to gratuitous goals. Chelsea, Manchester City and Arsenal boast a better assists/goals ratio than United, while the Reds are ahead of Liverpool in fifth. One may reasonably argue that United need a creative player and not a finisher.

Figure 1

In Figure 1, above, we look at  the past two seasons, where there is no correlation between points won and the assists/goals ratio. Apparently, the Premier League table does not discriminate goals.

Adding a great finisher like Depay can only help though – no United player has broken the 20 goal barrier this season. Of course, United has not created as many chances as its rivals so Rooney and Van Persie’s failure to score regularly can just as easily be blamed on United’s midfielders as the club’s strikers.

Another possible argument is that the fragility of United’s defence has been stopping the Reds from maintaining pressure in opposition half. Herein lies the problem – there are a multitude of factors at play in a team’s goal-scoring record and data cannot capture the precise mechanism. This is one reason predictive models, such as the ‘expected goals’ model, are ultimately fun but meaningless. The statistical methodology is shoddy but, more tellingly, there is simply no theoretical foundation.

Basic models, such as the one presented here by Data Rant, do offer a descriptive picture of the status quo. Clearly, only focusing on creating goals would be meaningless. The fact that United has only managed 11 set piece goals while Arsenal, having played one less game, put away 21 suggests that United should look at set piece specialists too – which, incidentally, Depay is.

Another way to force goals is by pressing the opposition. Ander Herrera is the only truly mobile central midfielder at United and partnering the Spaniard with a destructive player, such as Kevin Strootman, may allow the Reds to regain the ball in dangerous areas or run onto stray square passes.

Van Gaal is not infallible, but he has operated with a reasonable and rational plan over the past 10 months. Depay boasts many qualities, chief among which is that he is one of the most lethal free-kick takers on the continent. The statistics suggest that some value must be attached to dead ball situations as well. Van Gaal seems to be very aware of this.

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