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Data Rant: how many goals will United need this season?

September 2, 2015 Tags: , Data 21 comments
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Manchester United wrapped up business for the summer on Tuesday with the £36 million acquisition of Anthony Martial. Ed Woodward failed to significantly improve Louis van Gaal’s defence, but added two of the best young forwards in Europe in Memphis Depay and Martial. Meanwhile, midfield has been significantly improved by Bastian Schweinsteiger’s experience and Morgan Schneiderlin’s steel, while David De Gea’s service has been retained – for now. So where will United finish next May?

This column has previously noted the weaknesses in popular in predictive models, such as the expected goals approach (xG), so does not attempt to build a fresh model that spits out general predictions. Instead, Data Rant makes a few broad assumptions and then we discuss the possibilities that arise.

United is assumed to be just as solid defensively in the current season as last year. After all, there has been no personnel loss in defence, aside from the departures of reserves Rafael da Silva and Jonny Evans. Luke Shaw has started the season well, working towards justifying his price tag, while Matteo Darmian has been commanding down the right flank. Louis van Gaal has also persisted with a possession-oriented philosophy this season.

Elsewhere in defence, David De Gea must be affected by the ludicrously botched deal between United and Real Madrid. Still, the Spaniard now has a strong incentive to perform to the best of his considerable abilities this season, with the Spain national team’s number one jersey very much up for grabs. Good performances will also allow De Gea to leverage a better deal with Real next summer. Given these assumptions, it is not unreasonable to conclude that United will concede no more than the 37 goals that De Gea let in last season.

The question of goals scored is more tricky, given United’s inability to secure a new striker over the summer to go with the two youthful attacking acquisitions. However, the relationship between goals scored and league position is not all that strong, with a weak correlation over the past 10 Premier League campaigns. This is not all that surprising since it does not take into account each team’s defensive strength. Another factor is the inherent volatility in goalscoring.

Figure-1

The average number of goals scored by teams in each season fluctuated during the past 10 seasons, while standard deviation, which measures how widespread the teams’ goals scored are in a given season, varied even more wildly.

Figure-3

Figure-2

Goal difference by definition takes into account a team’s ability to defend as well. Indeed, there is a significant correlation between goal difference and league position. This is solid enough ground to make a prediction: specifically the goal difference required for a given position in the league table.

Figure-4

With these figures we can also compute the number of goals United need to score to reach a particular ranking since we assume that the Reds will concede, at most, 37.

Table

Note: for this table, a model from logarithmic regression has been used to account for the ‘kick’ in the higher league positions.

United scored 62 goals and came fourth last season so the model looks passable at the very least. Notice that reaching third or fourth is significantly easier than challenging for the title. The £100 million question, therefore, is the number of goals United will score this season.

As noted, there is no model – grounded in sound statistical theory and methodology – currently used that can accurately predict a player’s goal tally. There are simply too many factors in play. Take, for example, this hypothetical: suppose there are two Lionel Messis who perform exactly the same in any given game – the Messi at Old Trafford will probably score less than the Messi at Nou Camp because Barcelona has better players than United.

Instead, Data Rant observes that the current United squad will score 130 goals this season if Wayne Rooney and company manage to score exactly the same number as their career season high.

This is, of course, totally unreasonable on many grounds. Ashley Young, for example, will probably not play enough games to score eight goals. Elsewhere, players might do better though. Juan Mata’s career best of 12 goals in the Premier League seems feasible. However, Rooney’s form seems too dismal for the Englishman to score anywhere near the 27 goals he managed in 2011/12. But, then again, there is also a chance that Martial doubles his goal tally from last season.

Taking United’s goalscoring potential as a whole, the current squad can ‘win the league’ if the players perform to 78 per cent of their peak goalscoring potential. Since most players in the squad are too seasoned to realistically demand improvement, much of the responsibility probably falls on Depay and Martial. If United does well, the teenage striker’s fee may very well be justified at the end of 2015/16 Premier League season.

21 comments

Tom - September 2, 2015 Reply

is that calculation being made with or without Romero between the sticks?

Chris - September 2, 2015 Reply

More than the other team scores

Rohit-chaturvedi - September 3, 2015 Reply

First of all this is peach of an article. This must have involved lot of thinking and calculations. As a student of statistics I can acknowledge this is a piece of hard work.

Coming to the point, I concur goal difference is more important. People criticising LVG dont know that he does exactly these kind of calculations to form his strategies. Now as we have acquired a decent midfield we will definitely concede fewer no. of goals then last season. One only has to look at first 3 matches. We concede 0 goals and Romero had very few saves to make. We only conceded in fourth match where Romero should have saved atleast one of the goals. With DDG on board I think defence looks pretty solid. So we should definitely concede less than 37. So the inference is that it will all depend on how Rooney, Martial and Depay fare throughout the season. As you say Martial and Depay will be the vital cogs. So I hope that the 78% theory comes true. Also asking 78% from these players is, I think, not too much. 😉

Denton Davey - September 3, 2015 Reply

A lot of eggs in TheWayneBoy’s basket – if he’s not up-to-snuff, then what ?

Also, the “return” of DDG might serve to further solidify the defence which might mean that there will be more possession and more 1-nil-to-the-Mancs matches.

In the best of all possible LvG worlds, 62-for/37-against could morph into 70-for/32-against and that would probably yield something like 80 points for the season. WIll that be enough ?

Neil - September 3, 2015 Reply

Jay, this is really interesting stuff.

One of the points I would like to make is that the bumper TV deal has allowed all of the smaller clubs to strengthen throughout their sides, this in theory makes the league more balanced and produces as many “shock” results as possibly any other league in Europe. This upturn in overall quality for the small clubs means it is now harder to score goals than 10 or 15 years ago, when the Champions League money gave the so called bigger clubs a distinct advantage.

The bigger clubs now need all their best forwards in top form in order to score a lot of goals. City have Aguero and Silva, this is an example of needing top quality at the business end of the pitch in order to make consistent breakthroughs. Contrast with the likes of Liverpool last season, who had a downgrade in their forward players, for various reasons, and had a very poor season.

United have been far worse going forward under Van Gaal than I had anticipated, our passing tempo doesn’t match what is needed to beat 80% of the PL teams, we are too slow and it allows teams to always get 10 men behind the ball. Add to this a lack of pace in our forwards, and Rooney being past his best, and we will need a miracle to finish above 3rd place.

Depay and Martial are good signings but will need a couple of seasons before they can be fully settled and show their full potential. Conversely we may be poorer in goal output this season than last season, I think mainly due to issues at United but mostly due to other teams being better, we just don’t have the tempo and pace to break them down consistently.

denton davey - September 3, 2015 Reply

“Conversely we may be poorer in goal output this season than last season, I think mainly due to issues at United but mostly due to other teams being better, we just don’t have the tempo and pace to break them down consistently.”

Too much negativity – the big problem last year was the incredible over-dependence on MC16. THAT has been resolved to such an extent that Carrick is now part of a three-man rotation in midfield.

Similarly, the addition of Darmian and the blossoming of Shaw is a significant upgrade to the back-five, assuming that DDG gets his mojo back. BigManSmalling has been exceptional so far and, in contrast to many, I’m also quite bullish on Daley Blind – he plays kinda like Paolo Maldini or Rio, if only in the sense that his positioning is very good and he doesn’t need to leave his feet when defending.

The question of “tempo and pace” is in the eye of the beholder – surely the two new kids and Ander Herrera are big upgrades on Ashley Young (the man with no end-product) and TheAngel (the man who didn’t want to be here) and Falcao (the man who lost his quickness) and RvP (the man who lost his pace) and DannyTheLad (the man who wasn’t there when it mattered).

Playing Juan Mata is always a bit of a conundrum since he can produce magic with the ball at his feet but he is slow, though no slower than Andres Iniesta or David Silva. TheWayneBoy is the key and the issue – his raw speed seems to be OK (according to the various metrics that have been documented) but he’s lost his aggression. In that sense, the slower build-up/tempo of LvG’s system seems to have had a very negative impact on Rooney’s confidence – how else can you explain those two glaring non-shots against Swansea ?

Subterranean Steve - September 4, 2015 Reply

He’s been there over a year and van Gaal is still to get the best out of the attacking players he has had at his disposal, both individually and collectively – and there have been plenty of them.

Opti - September 4, 2015 Reply

Nice article!

Goal difference makes a difference… score 1.5 more goals / game than our opponents and we’ll do great… 1.0 more (i.e., 1-0 victories) may not be enough…

bobbynoble - September 4, 2015 Reply

Fucking statistics.

Let’s play football with passion, verve, flair and excitement.

Thrill me with an inch perfect, slide rule pass but don’t inflict upon me a dry, dreary, statistical analysis or ask “How many goals do we need?” The fact that this question has been raised and people are discussing it as if it requires serious, intellectual consideration, is quite depressing. It’s totally van Gaalian.

I doubt whether any of the great United players throughout history would have given tuppence for such a statistical analysis. Would George Best, Eric Cantona or Paul Scholes have given it any cconsideration? I doubt whether any of the managers except probably LVG and perhaps Dave Sexton would have given much thought to it either.

Sir Matt sent his teams out with, “Make sure that when you come back, you have scored more goalls than the opposion.” Of course, that was his final directive after his team talk and it is a simple enough comment, but then football is a simple game. Or at least it should be.

Let’s have more footballing Art and Entertainment, and less fucking ‘……ology’.

Unbelievable Jeff - September 4, 2015 Reply

Superb fella. Couldn’t have said it better myself

bobbynoble - September 6, 2015 Reply

‘Unbelievable Jeff’ = Cheers mate! Thought I was a voice in the wilderness.

Ed - September 4, 2015 Reply

bobbynoble – I realise this is, as the kids say, ‘meta’, but you’re seriously complaining about the subject of an article that you just read… there’s an easy fix. Don’t read it!

William - September 4, 2015 Reply

Yeah, Ed is right. The first word in the title of the piece is ‘Data’. This should be a fairly decent clue that this is going to be statistical analysis. If you don’t go in for that then don’t click.

I, for one, think that this is an excellent piece showing some interesting statistical trends. I’m sure that it isn’t meant to take the joy out of the game.

The two aren’t mutually exclusive.

bobbynoble - September 6, 2015 Reply

‘William’ dear boy, you’ve missed the point. This article would never have been written if LVG’s football had been any fucking good.

bobbynoble - September 6, 2015 Reply

ED. I doubt whether you or Jay Shon would have felt the need to write an article such as this if it were not for the crap goalless footy served up byLVG. It might be worthy of the attention of the chattering class of ‘educated’ fans but that only reinforces my point.

I could say, “, but you’re seriously complaining about the subject ofa response to an article that you just read… there’s an easy fix. Don’t read it!”

But I won’t cos you are the Ed.

Ed - September 7, 2015 Reply

bobbynoble – this is a very circular argument in danger of disappearing up its own arse 🙂 I see nothing wrong with delving deeper into issues surrounding United. Some people like that kind of analysis. You don’t. So be it. By the way I agree with your assessment that most of all United just need to play some more exciting football.

lambert cato - September 4, 2015 Reply

oh boy! We’ll be needing a lot of goals, cos with our current defense, we’ll be conceding a lot too.

Denton Davey - September 4, 2015 Reply

The “current defence” is an upgrade on last-year’s group if only because it will be better protected by Schneiderlin and Schweini and MC16. Last year, TheLads let in 37 goals and I’d expect that this year there will be fewer allowed and a few more scored. With regard to your main point, yeah.

The possession-game is geared to grinding out wins not playing fire-wagon “you score three, we’ll score four” which has sometimes been a UTD style – BUT not always (remember that after the ignominious 1-6 derby defeat, SAF had TheLads go all-out defensive and they put together a run of about a dozen clean sheets). Also, UTD only got to the 2008 CL final by parking-the-bus against Barcelona and winning on a wonder goal by the GingerNinja. How could anyone forget that ?

Subterranean Steve - September 6, 2015 Reply

Agree that United have, at times in the past, resorted to tactics which were hardly designed to produce free-flowing attacking football. However, these tactics were used in one-off situations eg against Barcelona.

Van Gaal has brought his philosophy to United with a style that fundamentally limits the opportunity for attacking, risk-taking football. It has become the norm not the exception. Historically, the quality of United’s football has generally been determined by the quality of the players available. Better players has meant better football.

Under van Gaal, very good players are producing very ordinary football, game after game. Something quite unique in United’s post World War II history.

denton davey - September 6, 2015 Reply

“Historically, the quality of United’s football has generally been determined by the quality of the players available. Better players has meant better football.”

That’s the point, though, isn’t it ? UTD’s “attacking players” just aren’t that good and a lot of players have been jettisoned because they are just too slow.

The hope-going-forward has to be that both Memphis AND Martial are both seriously good and seriously quick.

For me, the issue isn’t flat-out pace but rather quickness in the danger zone – LvG team’s end-product has lacked the incisiveness that comes from first-step quickness (and an ability to read that quickness by the guys who are “play-making”).

Like they say, the ball moves faster than any runner. It was fascinating watching Germany and Spain in the last few days – the Germans have a lot of “lightweight fancy-dans” (Ozil, Kroos, Muller, and Goetze) who are just about the same kind of personnel as the Spaniards feature with Silva and Iniesta and so on. In the front, attacking zone both national teams had one “hard man” – Schweini for the Germans and Costa for the Spaniards.

But the speed-of-thought/imagination of both teams was just thrilling to watch – but only when it worked out; when it didn’t work out then it was like watching paint dry (or grass grow). Not surprisingly the template for the Germans is LvG’s Munich while the template for Spain has been – and still is – LvG’s Barcelona. BUT, obviously, those national team/club sides are graced with players far superior to TheWayneBoy and AshleyBloodyYoung.

Subterranean Steve - September 6, 2015 Reply

At their peak players such as Denis Law and Michael Owen were brilliantly quick over five yards or so and that was a key factor in their prolific goal scoring.

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