Category Archives: World Football

PWP PROCESS SLIDE

The most accurate index you’ve never heard about: “Possession with Purpose”

I was messing around on the internet one day reading up on the “Expected Goals” metric that has become the darling of the stats world when I, like all great explorers before me, “discovered” this site called “Possession with Purpose“. On that site I found an analyst who was creating charts with R² values above 85%. In other words, I found an analyst who had created a metric which showed an almost perfect correlation between his index and the outcome of matches. That analyst’s name is Chris Gluck.

Let’s step back for a second and define a few things. Think of this as a brief history of stats in football: we started with “stats suck”, the only stat that matters is goals scored. From there we have progressed to “stats don’t tell the whole story” and “stats are like a bikini what they cover up is more important than what they reveal.” Since then, I have noticed that even traditional writers will now latch on to a stat, like say tackles made, and present it as if it had meaning all by itself “Denilson made 93/93 passes!” That’s where the average football fan is right now. Arguing over stats that may or may not have any meaning.

But there is a special brand of analyst out there who is just now starting to impress on the rest of the world that there might be another way. It started, as near as I can tell with a stat called TSR. Yes, TSR is both the publishing company for the original Dungeons and Dragons and a nerdy stat in soccer, “Total Shots Ratio.”

Total Shots Ratio is simply the ratio of shots taken to total shots. This metric was shoved into the limelight when Grantland published an article about it in August 2013. It’s funny to me, because in my time searching around for an analytic that showed strong correlation between one event and League table, I discarded total shots ratio early on as not passing my smell test. After all, teams like Tottenham and Liverpool routinely topped the TSR tables and yet sat lower in the actual table.

TSR was a decent metric and you often see me talk about how many shots Arsenal take compared to shots allowed because, well, because shots taken v. shots allowed shows some relative strength in each of those areas. For example, Arsenal played Barcelona a few years back and the Catalans took 19 shots to Arsenal’s 0. There was no doubt who dominated that match even if the score line was 3-1. How 3-1? Busquets own goal. You don’t even need shots to win games! But TSR’s usefulness was ultimately as a metric which led to another metric “Expected Goals.”

The problem with TSR is that it didn’t take into account the type of shot (header, footer) the distance of the shot from goal, what type of pass produced the shot (through ball v. cross), and other factors. Some very smart people, with a lot of time on their hands, started looking at those other factors and created the “Expected Goals” metric.

Michael Caley, a Spurs fan, created the most widely accepted “xG” metric in the analytic community. I’ve linked to his sortable fancy stats League table in his name. You should have a look at it, it’s quite fun. For example, using the shots data Arsenal are “bang on” the expected goals scored but are lagging a bit in expected goals allowed, about 4. Southampton on the other hand are doing better, defensively, than we would expect given their opponent’s shots locations and qualities. They have allowed just 15 goals this season and Caley’s model predicted they would have let in 20 by January 1st. If you saw the Southampton match against Man United the other day, you will have had it confirmed that Southampton rode their luck a bit: Juan Mata should have scored at least one of the two huge chances presented to him.

Expected Goals carries a strong correlation both to points per game (R²=.73) and goal difference (R²=.79) and is already setting the soccer stats world on fire. People are crafting their own xG metrics (I could do one pretty easily) and this is going to be something that football fans talk about for quite a while, I suspect.

But, and I know I shouldn’t do this but I do, why are Arsenal in 5th place on the League table if their xGR should have them in 2nd place? Bad luck? Errors? “Unexpected goals?”

It’s because the metric only looks at one outcome that it has this inherent problem. Goals are capricious. Look at Fernando Torres. He went from beast-mode to least-mode in the span of a few weeks. He was getting chances, he just wasn’t putting them away. And that was happening over and over again.

I’m not saying expected goals is crap, I’m just pointing out that teams can create great scoring chances and not put them away. That happens more often than we like to admit! Teams can also concede goals when they probably shouldn’t due to a number of reasons.

Which is why I was hunting around on the internet looking for different models. And boy howdy did I find one!

I’ve now spent several hours on the phone with Chris from Possession with Purpose and I had to have his model explained to me several times before I got it. Instead of looking at parts of the game, Chris broke the whole game into parts and then re-pieced them back together to form a more comprehensive analytics tool.

The way Chris explains it on his web site is elegant. The goal of a football match is to win, to earn three points. In order to do that you have to score goals. But in order to score goals, you have to create shots. Shots that are on target. And in order to create shots, you have to have penetrative possession. And in order to have penetration, you have to have possession of the ball and move the ball toward the opposition’s goal! In JPG format his theory looks like this:

PWP PROCESS SLIDE

Possession is 50% in football. Forget the possession numbers you see all the time, each team will have an equal number of possessions in a game. Some possessions may be longer than others but even a team like Arsenal eventually concede the ball.

Ball retention, on the other hand, averages about 79% in the Premier League. And from there, 25% of that 79% pass completion rate are passes which create goal scoring opportunities. Only 15% of those 25% passes in the opposition final third result in shots, 32% of shots in the Premier League are on frame, and 32% of those shots on goal are scored.

This is how a coach would look at the game, this is how a coach does look at the game, Chris Gluck is a coach and has coached at many levels of football throughout his life. So, it’s no surprise that Chris created a tool which measures more than just expected goals.

Just to put this philosophy another way, the point of offense in a football match is to (this is a quote from his site, linked above):

  • Gain possession of the ball
  • Move the ball
  • Penetrate the opponent’s defending final third
  • Generate a shot taken
  • That ends up on target and,
  • Gets past the keeper

In order to measure those things, Chris looks at the following measurable events (again, this is a quote from his site):

  1. Possession percentage
  2. Passing Accuracy across the Entire Pitch
  3. Passing Percentage within and into the Opponents Final Third compared to overall possession (i.e. = Penetration)
  4. Shots Taken per Percentage of Penetration
  5. Shots on Goal per Shots Taken
  6. Goals Scored per Shots on Goal

But that’s only half the game. The other half of the game is limiting the opposition’s ability to do all of those things to you!

And if you take those two metrics together, his Attacking Possession With Purpose Index (APWP) and his Defending Possession With Purpose (DPWP) together you can form a Composite Possession With Purpose index and that index has an R² value after week 21 in the English Premier League of…. wait for it… .92.

That is absurdly accurate and along with his body of work so far a major reason why he was asked to present at the World Conference on Science and Soccer. Now, before you run off and try to create your own index using this idea, you should be aware that Chris retains Copyright and PWP is Trademarked. Ok? Don’t be a douche.

Chris created a composite index of the English Premier League for an article he wrote just yesterday.

As you can see, his index matches very closely to the League table.  There are two teams (Chelsea and City) who have pulled away from the pack with regards to their ability relative to the League average. Below those two teams are a group of three (MUFC, Soton, and Arsenal) who are fighting for third and fourth place respectively.

Looking at just offense, we see why Arsenal are second on the “expected goals” table: Arsenal are very strong offensive team.

Remember, this is measuring pass success rate, pass success rate in the final third, the ratio of shots generated by those final third passes, the rate of shots on goal, and the goals scored. By those measures, Arsenal are easily right up there with teams like Man City and Chelsea.

The problem at Arsenal is defense.

As we know from watching matches this year The Arsenal are struggling with team defense. It’s something that Naveen has pointed out several times in his tactics column and a fact that shows up here in Chris Gluck’s DPWP index which has Arsenal with only the 8th best defense in the league.

Take the two metrics together and you can see why Arsenal are in 5th place: their offense is good enough for 3rd but their defense is bad enough for 8th. Possession With Purpose isn’t just looking at shot ratios, it isn’t just looking at shot locations, it is looking at all of the qualities that go into attack and defense. When we do that, we see that Arsenal are about exactly where they should be in the League table, 5th, because their defense isn’t stopping the opposition from getting penetrative passes, shots on target, and scoring goals.

I quite like the Possession With Purpose index. It’s accurate. Crazy accurate. And it uses the game’s most vital stats while eschewing the less important stats that people tend to think are important but aren’t. That’s a topic we will cover a bit tomorrow.

Until then.

Qq

Follow Chris Gluck on twitter @chrisgluckpwp
Chris hosts his own web site possessionwithpurpose.com and also writes for the Columbian and Stumptown Footy on SBNation.
All words from his site are COPYRIGHT, All Rights Reserved. PWP – Trademark

Arsenal-v-Manchester-United

McNair breaks Wilshere’s ankle and it’s time for the FA to act

Jack Wilshere had surgery this morning to repair an ankle wrecked by Paddy McNair in last weekend’s match between Arsenal and Man U. The match was billed as a clash of titans but in the end it was a clash of studs, that went unpunished, which decided the game against Arsenal and decided Wilshere’s season. It was an ugly tackle which drew little opprobrium from the press, draws ridicule of the fans when they mention it, and which has drawn absolute silence from the Football Association. Wilshere will be out for three months recovering from that tackle and it’s high time that the Football Association takes steps to ensure this doesn’t happen again.

First, this just needs to be said: Pat McNair broke Jack Wilshere’s ankle. The press won’t ever put it that way, usually opting for the passive voice and incorrectly phrased “Jack Wilshere broke his ankle” but it wasn’t Wilshere who broke his ankle, is was McNair. In case you haven’t seen the tackle, here’s the video evidence:

Wilshere did not break his ankle, McNair did.

McNair’s tackle was easily a red card and yet match official Mike Dean didn’t even blow for a foul. Sadly, this type of tackle goes unpunished every weekend, many times over, and it’s ruining English football.

This is where the Football Association needs to step in and bring some sense to the game. Several years ago Major League Soccer was plagued by this same problem — play was too robust, the officials weren’t seeing the fouls, and players were getting severely inured — and they solved the problem by simply instituting post-match video review and retroactive punishment.

MLS reviews matches and any time a player is deemed to have acted recklessly or with excessive force, they fine and ban the player. The whole process is refreshingly open, with videos of the incidents put directly on the MLS web site.

The scheme has worked, in my opinion. Tackling hasn’t disappeared from MLS football, hard tackling is even still a part of the game over here, but tackles which cross the line from hard to excessive, tackles like McNair’s tackle on Wilshere, the league steps in and bans the offending player. Can you imagine the FA putting a video of Man Utd’s Pat McNair breaking Wilshere’s ankle, along with a press release of the punishment meted out, on their web site?

Instead, in British Football, players like Jack Wilshere are punished for their talents. Jack Wilshere is a prodigiously talented young player. A man who has the close control of a player like Lionel Messi but who is playing in a league which doesn’t value that talent and instead lauds clod-hoppers like Pat McNair for their “fighting spirit.”

For years, the FA have sought in vain for an answer to the question “why haven’t England done well in international tournaments?” They have blamed big clubs for not creating enough English talent and not giving Englishmen a chance at the top level. But the problem isn’t that the big clubs don’t play enough Englishmen, the problem is that the FA doesn’t do enough to protect the top talent in the Premier League. Lionel Messi would never have developed into the talent his is today if he’d had to spend 2 years of his football career, two years from age 18-22, on the treatment table instead of on the pitch. That’s exactly what’s happened to Jack Wilshere.

Wilshere was just returning from injury this year and starting to blossom into a star midfielder for both club and country before his season was effectively ended by a wild tackle from Pat McNair. If the Football Association cared one iota about English football, they would put an end to this yob culture which celebrates season ending tackles. They won’t because they are part of that culture and they are complicit in every injury that results.

Qq

I SAID NO PEPPERONI ON MY PIZZA, ANDY

Man U and Tottenham’s foul play prove that referees need help

Football, more than nearly any other sport, relies on referees to get the balance correct. After all in a sport where teams routinely win by a single goal, a single bad call can mean the difference between winning and losing. And after this weekend’s results one thing is very clear, the referees in the Premier League are not getting the balance correct and desperately need help in the form of video replay.

In the Villa-Tottenham match, referee Neil Swarbrick gave a red card to Villa’s Christian Benteke for raising his hands to Ryan Mason’s face. It was exactly the wrong call and given for all the wrong reasons.


In the build up to the card, Benteke was shielding the ball when Erik Lamela tried to shoulder barge him off. The smaller Spurs man comically bounced off of Benteke and crumpled in a heap on the ground. Lamela got up and rushed Benteke trying to win the ball back with a wild tackle and as he passed the Belgian lashed out with his arm and looked to have caught the Villa man in the face.

Meanwhile Lamela’s Spurs teammate Ryan Mason steamed in and was all hands and feet trying to get the ball and at the exact moment that Lamela looks to have struck Benteke’s face, Benteke turned around to confront his assailant. Mason got in Benteke’s face, headbutted him, and then when Benteke had the temerity to raise his hands to push Mason away from him, Mason grabbed his face like… well, like a liar… and pretended he was injured. Seeing his teammate mortally wounded, Erik Lamela did the thing that must come naturally to him, and ran over to the referee, eyes wide at the horror he’d just seen, and brandishing an imaginary card demanded that Benteke be sent off.

Swarbrick took Lamela’s bait — hook, line, sinker, and subscription to Bass Pro Monthly — and after a brief conference with his sideline official showed Benteke a red card. The problem here is that it was always going to be Benteke who got sent off.

The reason is simple, the Premier League and their referees reward aggression and punish retribution. They always have as long as I’ve been watching. Remember when Arsenal’s Gervinho was fouled in the box by Newcastle’s Joey Barton, then Barton screamed at him and hauled him up off the ground by his shirt and when Gervinho put his hands up to get this monster off him, Barton collapsed on the ground like his face had been ripped off. And in a mirror of Spurs man Lamela wild-eyed and looking for the referee to punish, Barton’s teammate Steven Taylor ran straight to the referee, gesturing as if Gervinho had elbowed Barton. Gervinho saw red, Barton saw a pay rise.

I’ve seen this happen countless times, Patrick Vieira was sent off for a confrontation on Dennis Wise after the Leicester man tackled Robert Pires and then yelled at Pires to get off the ground. Jeremy Aliadiere was sent off for touching Javier Mascherano’s face after the Argentinian had made his umpteenth brutal tackle on the Frenchman. Too often this happens that referees allow aggressive play and then punish the opposition for standing up to these bullies.

The formula to get a player sent off in the Premier League is simple: aggressively harass the opponent, wait for the opponent to attempt any retribution, and if he does collapse in a heap on the ground like you’ve been shot while your teammates run straight at the official eyes wide at the injustice of it all.

After Benteke was sent off, Tottenham stormed back and won the game 2-1. All the talk this weekend has been about Harry Kane’s free kick which won the match, but it was a poor referees decision which cost Villa three points. Let’s hope Villa avoid relegation by more than three points or it could be a decision which cost the club and supporters millions of Pounds.

Meanwhile in the earlier match, Michael Oliver had a different kind of nightmare. The kind of nightmare where he refuses to award three stonewall penalties.

The game was Man City versus Man United and Man United were outclassed in every position on the pitch: Yaya Toure dominated the midfield, Sergio Aguero dominated the United backfield, and Vincent Komapny dominated the United forwards. United’s frustration grew until, in the 39th minute, Chris Smalling got himself sent off for two absurd fouls.

Playing against 10 men, City took the game into another gear and started creating good chance after good chance. The first came almost immediately after Smalling was sent off: Fellaini was filling in at center back and Aguero collected the ball deep in the penalty box. Fellaini, because he’s a terrible defender* kicks Aguero’s Achilles, Aguero goes down (as you do when your Achilles has been kicked because that hurts) and Fellaini looks at referee Michael Oliver. Oliver swallowed his whistle.

United sorted out their back line but City were still on top of their local rivals and on the stroke of half-time had a second stonewall penalty turned down. Yaya Toure beat the sleeping Rojo to a ball flipped over the defense, and Rojo went through the back of Toure, between his legs, and maybe got a nick on the ball as he hauled the Ivorian down.

People comically don’t see this as a foul because “Rojo got some of the ball”. There is no “got some of the ball” rule. If you take out your opponent, who is in an obvious goal scoring position (as Yaya Toure was), with a tackle from behind – going through the man to win the ball – and you bring the man down so that he can’t recover the ball and score? That is a red card and a penalty.

The third, however, was possibly the most egregious of them all. Referee Oliver is staring, unobstructed, at Kun Aguero as he dribbles across the United box. He then watches as Aguero is fouled by both Carrick and Fellaini and refuses to award the penalty. Fellaini even makes the face that proves he is guilty.

English football is no longer a game played behind closed doors, un-televised, and only reported on by a handful of scribes and witnesses in the stands. These games are now broadcast all over the world, with instant replay, and fans are able to capture moments on their vine and tweet them out to their followers. In short, every aspect of the game is now viewed through the lens of technology. Every aspect save one: the view of the referee. It’s time that referees are given the same benefit as the rest of the world. It’s time that referees are given instant replay.

Since I know this idea engenders a visceral reaction I will suggest that the FA and PGMOL start simply, with post match red-card reviews. Major League Soccer does this. Ex-post facto they punish players who commit red card offenses which the referee saw and punished with only a yellow card. They also punish players who got away with fouls. In the Benteke situation above this means that Erik Lamela and Ryan Mason would receive retroactive red cards for their actions. This doesn’t help Villa get their three points back, but it does put all the players on alert that their bad behavior will no longer be tolerated. That players will no longer be able to get away scot-free with endless provocations.

After that, I think managers should be allowed to demand a single, or maybe one per half, referee adjudication using video replay. This would solve the problem of Michael Oliver not calling a penalty in the Manchester Derby. At least I hope it would force Oliver to call those plays correctly. There’s still no guarantee that the referee would change his mind.

But at least we would all be on the same page and right now, referees in the Premier League aren’t even i the same paper. They are still using papyrus.

Qq

*I say this for the benefit of the three Arsenal fans who still think he could play defensive midfield for Arsenal. He can’t. He can’t because he has almost no understanding of how to defend. His idea of defense is “sticking a foot in”. So, unless you want to risk conceding a penalty every time you play, you don’t play Fellaini as a defensive midfielder.