Things We Think We Know About Football – July 2013

Some days it’s good to take a step back from the daily deluge of information and try to organize what you think you have learned recently. I’ve been writing regularly on football analytics for about six weeks now (and off and on for seven months), and I’d say half the topics I’ve covered are based on poking around the data, and the other half are riffs on insight from other writers. I certainly feel a lot smarter about the game and about analytics than I did before, but what do I really know? And more generally, what do people in the analytics community think they know about the game that maybe they didn’t a month or two ago?

Crosses Are Bad
There are a couple of references for this that I really like. The first ones are from WillTGM, who looked at crossing generally as well as in the context of Liverpool, last summer. Will’s task was to look at whether Liverpool chose to play a heavy-crossing game tactically the year Kenny Dalglish was fired, and then to investigate whether that type of tactical choice is particularly effective at generating goals. I’m linking to the whole category of pieces he did, because they are really well written, explore a number of different aspects, and should basically be required reading for anyone interested in the topic from an analytics perspective.

Will concludes that open play crossing is extremely difficult (20.5% accuracy vs. nearly 34% from set pieces), and that most teams aren’t very efficient at converting them into goals. Liverpool did indeed choose to cross the ball an awful lot that season, but goals did not pour in as a result. In general, nobody is effective at turning crosses into goals. (I’m shortchanging the work a bit here when I summarize – he covered all sorts of useful stuff. Just go read them.)

theowalcott_crossThe second one is from @footballfactman, looking at Theo Walcott’s crossing, which is deemed a) generally inaccurate and b) surprisingly devastating. Paul digs a little deeper and discovers that most of Walcott’s assists are from short (presumably low) crosses and pullbacks. In fact, from having watched Arsenal constantly, I would guess the majority of Theo’s crosses period have been low and hard, and he had an almost psychic relationship with RVP and that near post run. This is dramatically different from what you would typically get from Golden Balls or Leighton Baines. Because of this style, they are easier for defenders to simply cut out and clear, but they also result in a reasonable amount of goals when completed. It would be interesting to see how many of the cutouts from this type of pass result in possession going right back to the attacking team, since they don’t see very controllable.

The point here is that crossing is really hard. Even Baines, who is one of the best in the Premier League at completing them, only succeeds in finding a teammate 30% of the time.

Headed Shots Are Bad
This one is fascinating because if you do the surface analysis, it looks like this.


That image is taken directly from Colin Trainor’s seminal examination of the subject , and if you stop at the surface examination you suddenly think “WOW, headers are the way to go. They are just as accurate as ground shots, they are three times less likely to be blocked, 10% less likely to be saved (based on percentage comparison), and 33% more likely to score a goal. Those numbers are massive!”

Not so fast, my friend.

This… this is the area where good, detailed analysis comes into play.

When controlled for location as Colin did, headers are considerably worse at scoring than ground shots in every single spot on the pitch. The only thing that makes headers look so amazing is that they are all taken relatively close to the goal. Meanwhile, ground shots come from everywhere (even though they shouldn’t – that’s a topic for a different day).

Headed Passes Are Bad Too
This one came up as a result of the piece I wrote complaining about how big forwards don’t fit into Arsenal’s general strategy, so why does Wenger keep buying them?!? Anyway, it sparked a bigger discussion that not only deserves its own article, it also indicates a need to change the way we break out and display passing stats. Here’s the quick hit:

Player Ground PS% Ground Pass Head PS% Headed Pass Total PS%
Giroud 77.9% 430 39.3% 234 64
Dzeko 79.5% 517 32.1% 131 69
Ibrahimovic 78.5% 1165 41.4% 111 75
Van Persie 86.4% 831 39.6% 91 80
Lewandowski 78.9% 560 42.3% 123 72
Carroll 81.8% 340 38.6% 321 61

*pause for effect*

Headed passes from forwards are half as likely to be completed as ones on the ground.

There is sense to this. The hits that players take when trying to head the ball would be instant fouls if anyone did the same when they are standing on the ground. Additionally, the quality of the aerial ball itself is so much more important than the quality of a ball played to your feet. A headed pass is a first-time pass, every time. Oh, and unlike a pass along the ground, the trajectory of the ball now exists in three dimensions instead of two. Heading is just really bloody hard.

Andy Carroll has nearly equal amounts of attempted passes with his feet as his head – of course he’s going to look terrible. Maybe the problem isn’t with passing skill with the big forwards, maybe the problem lies with the approach?

Obviously it’s an important part of the game, but heading the ball simply isn’t something you want your offensive players to do a lot of if you can help it.

Passing Bleed Is Bad
I discussed this in brief when I talked about Olivier Giroud at Arsenal, but it deserves application on a broader scale.  Central midfielders pass the ball 50 to 80 times a match. A 5% difference in player completion percentage is 3-4 passes a match. A 10% difference means 6-8 more failed passes in the central midfield, and at that point it really starts to matter. It also has a trickle-down effect into what kind of passes your team has to make to be safe, and what kind they are capable of making to attack (think long, diagonal balls to wide forwards on the counter-attack).

Passing percentages vary widely due to tactical considerations, but if you control for those types of things, you want the best passers possible all over your squad. Choosing a player with a 5% lower success rate that makes up for it in other areas is fine, occasionally. However, 5% worse across an entire team that passes 500 times a match results in 25 more possessions for the opposition, every game.

Lesser passers bleed away possession to the opposition, and eventually that bleeding will lead to goals.

Football is Inherently About Percentages
It’s true, and the game does not give a damn whether people care about this or not, because it is imposed as one of the basic structures of playing football.

I know that’s statty/geeky as hell, but it is a simple, obvious truth. The sooner this is accepted, the sooner people can go about applying the principles to make their teams better.

Conclusion: Strategies that revolve around crossing and heading are hugely inferior strategies.

Look, this isn’t my conclusion, this is what math says.

Crossing is hard.
Heading is hard.
Passing the ball as a header? Also really hard.

So why would any manager choose to do it regularly?

I have two theories on this, from two different angles.

1)      This approach makes sense if it is rare and teams are unprepared for it. If the vast majority of the league plays normally, and your squad employs a physical, aerial approach, teams may be uncomfortable playing that style of football and you have an advantage. However, once a number of teams play this style, counter-strategies (like putting four centerbacks in the lineup across the back line and/or playing all your tall players) come into play that destroy this.

2)      It’s cheaper to play this way than competing with other teams for “normal” players. I might believe this if I didn’t see how much Sam Allardyce and especially Stoke had spent on players in the last five years.

So uh yeah… I don’t think either of my theories make logical sense anymore. Therefore I honestly don’t know why any smart manager, and especially an analytically savvy one, would choose this avenue for their team.

Mixed Strategies Are Not Only Good, They Are Vital
So this is where it gets tricky. Crosses are bad. Balls in the air are bad. Headed shots are inferior to ones on the ground from the same location.


Image from

Image from

You need to be able to perform all of these at a reasonable level in order to make your opponent respect they are part of the arsenal. You need to threaten from wide to keep the defense from simply packing the box so tightly nothing ever gets through.  You also really need to be able to head the ball well to have a chance at scoring goals from longer free kicks and corners.  So even when they aren’t deployed as a primary avenue of attack, these things need practice, and work, and players who have the skill to turn them into threats.

However, when you bring it back to percentages, they don’t have to be the primary or even the secondary options. You need to enact them just enough that your opponents don’t know what’s coming all the time.

The interesting thing is, when applied in this fashion, the effectiveness of these lower percentage plays often goes up. Teams get so focused on shutting down the central passing and lateral movement, that they overbalance and leave the break to the byline open. Suddenly defenders are scrambling to prevent a free break on your keeper, and the cutback to the penalty spot is completely open.

Central defenders’ legs get tired from chasing speedy guys around for 75 minutes, and they no longer defend aerial crosses to the far post as well. Chicharito/Dzeko have a late-game feeding frenzy.

The short corners you keep taking pull out not just one, but two extra men from the box, and that was the guy that was supposed to mark the player on your team who just got an open header.

So yeah, all those things listed above are bad, but… you can’t just play it on the ground all the time, or your team becomes predictable and easier to stop . Mixed strategies aren’t just recommended, they are vital when it comes to success. This is true whether your team is trying to pass the ball into the back of the net every game, or whether your manager has procured Andy Carroll as the pack horse for their own special brand of hoof ball.

Brain dump, finished.

Class dismissed!


What the Hell Are We Doing? Goals and Transfer Shopping

ss_moneyball_gunshipToday’s piece is inspired by the early summer transfer signings. The goals in the title don’t refer to actual goals that are scored on the pitch, though that’s what I normally write about. Today, the word “goals” is referring to team milestones.

Literally, what is your team trying to accomplish this year?

Are they simply hoping to survive in the top tier of football? To snuggle deep into mid-table obscurity? To compete for a spot in Europe? To get into the Champions League? To win the Champions League?

All of those goals have different requirements in terms of what kind of players your team should be buying, how much they should be spending, how many players are needed in the first place, etc. Everything in football has a cost, not just in terms of £££, but also in terms of expenditure.  Money is a resource, but so are effective player minutes. At some point, rotation becomes absolutely vital, even for smaller teams.

Want your team to make a deep cup run or two? You either need a bigger squad, or you can expect it to cost you places in the league. Given how much the English Premier League now pays out in prize money based on league finish, that money adds up quickly.

Want your team to compete for the Europa League as well? That will burn a lot of player minutes. The more minutes your team plays, the more likely they are to get injured. If your first team is absorbing all of those minutes, then your best players will be the ones who get injured, and that has an effect on every other competition you are in. Also, even if nobody really mentions this, fatigue is totally a thing.

Continue reading

5 Hot Transfer Targets from Spain That You Need to Know

Iago says, "Welcome."

Iago says, “Welcome.”

Welcome back to another set of transfer dossiers. To those who are new to this series, you can check up on the German targets here, plus France part 1 (including Payet, Mollo, and Cabella) and  and part 2 (including Ben Yedder, Alessandrini, and Boudebouz). The point of this series is to use statistics to help unearth excellent players that you might have never heard of before. By focusing on certain key metrics, it becomes possible to see players with high levels of potential well before they become stars, which in turn means you can sometimes find superb bargains in the transfer market.

The end of this piece includes a review of Liverpool target Iago Aspas, but first we’ll look at the guy who lead La Liga in Schrodinger’s Goals this season…

Continue reading

Can Goal Scorers in Lower Leagues Succeed in the English Premier League?

[Author’s Note: Usually when I write analysis, I try to be definitive in what we can and cannot say. The point of doing this at all is to learn more about the game of football, and part of the learning is designing a solid methodology that lets you make declarative statements.

Sadly, today’s piece doesn’t quite let you come to definitive conclusions. As much as I want to say, “Yes, these things are true!” in this case I can only say, “I think these things are true and the data mostly agrees.” Despite all that, I think this piece adds to the general knowledge, and I hope you enjoy.]

Jordan_RhodesTeams should have bought Jordan Rhodes. Premier League teams, I mean.

They probably should have done it after he scored 7 goals in 14 matches at League Two Brentford at age 19. Instead, Huddersfield bought him for £888K. They certainly should have bought him when he put up a 19G/7A season in 45 starts for Huddersfield in League One at age 20. And again after a 16/1 in 28 starts at age 21. And AGAIN after a 37/3 in 37 starts at age 22.

You see, Jordan Rhodes is a massive outlier. Players who produce numbers like he did at Huddersfield – scoring goals at a rate of one per game – are exceptionally rare. It’s rarer still that they do it at such a young age. As something that is rare in the game of football, and with a skill so valuable, you would have thought that one of the Premier League clubs would snap him up as soon as he came to their attention.

None of them did.

Continue reading

Transfer Dossiers – Ben Yedder, Alessandrini, Boudebouz, and a Dude Named Saber

Greetings, and welcome to another edition of Transfer Dossiers. In this series, I take a statistical look at potentially overlooked or just plain interesting transfer targets in the major leagues. I covered the first half of the players from Ligue 1 here. They include Payet, Mollo, Cabella, and Feret, so if you are interested in them, clique ze link. [Note: I also looked at Bundesliga value targets here.]

Today I’m going to look at a couple of young goalscorers, as well as an attacking midfielder that was rumoured to be on his way to Liverpool last summer, a transfer that – like most of Liverpool’s summer transfers last year – never quite happened.

[Note: I have added an explanation for the abbreviations of stat categories at the bottom.]

Continue reading

Shoot. The. Ball! Or Efficiency and The Shot Limit

Earlier this week, I looked at Luis Suarez’s offensive efficiency in comparison to other star forwards around Europe. At some point in the future, we’ll probably combine all of the numbers I examined to come up with a single efficiency metric (sort of like OPS in baseball), but for now you can only say Suarez creates a lot of shots and key passes, loses the ball a lot, and is comparatively bad at turning his shots into goals.

The larger question here is this:

Why does efficiency matter?

In this particular case, we’re talking about offensive efficiency and it’s worth taking a second to step back and think about the endgame.

How do you win a football match?

Score more goals than the opponent. It’s still a simple game, right?

Well, there are two parts to that statement. 1) Score goals. 2) Stop the opponent from scoring goals. Ignore the defensive side of the equation for now, and you come up with the objective for the offense: Score goals.

Now, how do you score goals?

Shoot. The. Ball.

Still obvious, right? But what if I told you there’s a limit to how often a team can expect to shoot the ball?

Continue reading

The Suarez Conundrum

Image from

Image from

Liverpool have an issue this summer, and that issue is whether or not to sell Luis Suarez.  Every other decision they make about player personnel is secondary, partly because of the amount of money involved, and partly because of the impact Suarez has on the entire team when he’s on the pitch.

Before addressing the question of whether Liverpool should sell directly, I want to take a look at Suarez’s production. Fans on Twitter have been comparing him to Falcao, Cavani, Ibrahimovic, and Lewandowski as one of the world’s best forwards. Despite this year’s goal tally, I find myself sceptical of those comparisons, but was happy to look at the data and see what it had to say.

Continue reading