Compromised numbers: Why the statistic you see may not be actual possession


One of the amazing statistics to come out of last Wednesday’s UEFA Champions League match was the possession number. Barcelona was reported by UEFA was having held the ball 72 percent of the time, an amazing figure against a club of Chelsea’s caliber. For those who have tried to find significance to correlations between possession and victories, the number must have been both remarkable and beguiling. After all, Barcelona lost, giving more credence to the hypothesis’ main qualm: What if one team doesn’t care about holding the ball?

The next day, the possession story got even more confusing. Supreme stat overlords Opta reported that Chelsea had only managed 20 percent of the ball. What? Even less time in possession? How freakish is this data point going to get?

That, however, is not the story. At least, it’s the story in light of what Graham MacAree notes at Chelsea fan site We Ain’t Got No History. As he’s found out, Opta seems to be miscalculating possession; or, better put, Opta is not reporting a number consistent with the normal expectation for a possession stat.

The normal expectation: When one team has the ball, they’re in possession. I think we can all agree on this, right? This still leaves a lot of gray area. For example, who gets credit for possession when midfield chaos leaves neither side in control? Does one team get possession on a goal kick, when most goal kicks lead to 50-50 midfield challenges? And more broadly, what happens when play is dead but the game clock is running?

I’ve always assumed this is like a chess clock. When one team controls the ball, you hit a button that sends their dials turning. When the other fully regains possession, you hit a button. One clock stops. The other starts running. Those in between moments? They’re governed by one rule: Until possession changes, don’t touch anything.

That, apparently has nothing to do with Opta’s calculations. In fact, Graham’s research suggests Opta doesn’t even run a clock, which may be why they never report possession in terms of time. Instead, the relation between reported possession and total passes suggests Opta just uses passes. As Graham found out, if you take a team’s pass attempts a divide it by the game’s total attempted passes, you have Opta’s possession stat.

What does this mean? Let’s take a totally fake scenario. Barcelona plays three quick passes before trying a through ball that rolls to Petr Cech. It all takes four seconds, while Petr Cech keeps the ball at his feet for eight seconds before picking it up, holding it for five seconds, then putting it out for a throw in, which takes eight more seconds to put back into play.

Despite Barcelona having possession for only four of those 25 fake seconds, they’d have 80 percent of Opta’s possession (three good passes plus one bad, while Chelsea had only Cech’s unsuccessful pass). A logical expectation of a zero-sum possession figure would have that as either 16 percent or (if you credit the time out of play as Barça’s, since they’d have the ensuing throw) 48 percent Barcelona’s. Or, if you do a three-stage model (that’s sometimes reported in Serie A matches), you’d have 16 percent Barcelona, 52 percent Chelsea, and 32 percent limbo/irrelevant.

Of the three methods of reporting possession, Opta’s bares the least resemblance to reality; or, it’s the one that deviates furthest from what we expect from a possession stat.

Ironies being a thing these days, there are two here. First, Opta is the unquestioned leader in soccer data management. How could this happen?

Second, Opta isn’t trying to hide their methods. In fact, they’ve published a post on their site detailing not only their practices but their motivations and research, an investigation that found their approach “came up with exactly the same figures (as time-based methods) on almost every occasion.”

You would think two curmudgeons like Graham and myself would have found this, right? Graham had a reader point it out to him, while a representative from Opta magnanimously pointed me to the piece without the seemingly necessarily indignation of explaining how a Google search works. After all Graham’s work and head scratching – after my lack of work and similar head-scratching – we could have just gone to Opta’s site.

“We try to be as transparent as possible with this stuff,” Opta said when I asked them about it. Certainly, they should be commended being so up front about their methods. After all, they’re a business that makes money off their work. They don’t need to give away their secrets.

But that’s a secondary issue. The main one: Why is a data house like Opta, reputed as the industry standard, taking this short cut? Or, why haven’t they renamed their measure? Granted, the perception that it is a shortcut may have more to do with our expectations than their intent, though based on their defense in the post, it’s clear they do see this as an accurate way of describing possession.

Still, the number they publish is completely redundant to the raw passing numbers also distributed. Why put the measure out at all if not to check a “possession stat” box on a list of deliverables?

Opta’s possession stat shouldn’t be cited in reporting, and if it is, the word “possession” shouldn’t be used to describe it. Reader expectations for anything labeled “possession” are drastically different than what Opta’s producing. The number is confusing to the point of being misleading. It’s becoming counter-information because of its poor packaging.

Even though Opta’s post on the topic is 14 months old, most will be surprised to hear this “news.” It’s disconcerting for anybody who is hoping a SABR-esque revolution’s on the horizon. Almost all of the huge volume of data to which we have access has been useful, but where people are expecting something akin to linear weights to be published tomorrow, we can’t even agree on the terms (let alone the significance of them).

Graham probably puts it better:

I’m completely fine with keeping track of passing volume – I’ve done it before myself. What’s frustrating, from an analyst’s point of view, is that we’re being sold a dud. A statistic that ostensibly measures possession measures something that is not possession, and gets repeated as authoritative anyway.

And people wonder why football statistics don’t get taken very seriously.

Report: Ibrahimovic to sign with MLS next week, LA Galaxy likely landing spot

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It appears Zlatan Ibrahimovic will finally be taking his talents to the United States.

According to a report from ESPN FC, Ibrahimovic has played his last game for Manchester United, with the club ready to let the Swede out of his contract in order for him to sign in Major League Soccer. While it’s not 100 percent clear where Ibrahimovic will end up, the report states the Galaxy are the leading contenders for his services.

[READ: International preview, what to look forward to this week]

Ibrahimovic certainly comes to the U.S. with a rich pedigree, with a trophy room full of league titles and UEFA Champions League titles.

But there are questions hanging over Ibrahimovic. The 36-year-old is coming off a torn ACL and whether he’s healed now, 12 months since the injury, he’s made just five appearances for Man United this season, with four of them coming off the bench.

With many MLS clubs moving towards signing younger, up and coming talents, especially from South America, can Ibrahimovic keep up in a physical league, coming off a major injury and at his age? It’s likely he can make an impact, but considering the kind of money he’s likely to be on, it will be tough for him to be worth it without bringing an MLS Cup.

If he does sign with the LA Galaxy, it would be a massive statement back to their new noisy neighbor in LAFC, after the expansion club made waves signing Carlos Vela as a Designated Player and Bob Bradley as head coach. Ibrahimovic will have to quickly gel with Sigi Schmid’s squad, including with Giovani and Jonathan Dos Santos in midfield.

Wilshere could have left Arsenal last August

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It’s hard to imagine an Arsenal team without Jack Wilshere on the books, but it nearly came to be during last summer’s transfer window.

Speaking openly in England’s training camp this week, Wilshere detailed how Arsenal boss Arsene Wenger approached him one day in August and told him the England international wasn’t in Wenger’s plans.

“It was an honest conversation,” Wilshere told The Guardian. “It had been boiling up for a while. Everybody knew I had a year left on my deal and had been out on loan, got injured and wasn’t really in his plans. He just said: ‘At the moment we are not going to be offering you a contract so, if you can get one somewhere else, you can go.’”

Wilshere said that he looked around but ultimately wanted to win his place back in the Arsenal first team, and he did so by November, after mainly playing in the Carabao Cup and UEFA Europa League through the first three months of the season.

This week, Wilshere earned a recall to the England National Team for the first time since the Three Lions’ disastrous defeat in Euro 2016 to Iceland and he’s played 31 appearances this season in all competitions, the most since the 2013-2014 season, showcasing a new-found fitness level.

That being said, Wilshere hasn’t found the form for Arsenal that earned him plaudits in the past from Xavi Hernandez. Wilshere looked off the pace in Arsenal defeats to Tottenham, Ostersunds and Manchester City in February, failing to make an impact in his central midfield role.

Wilshere has three months left on his contract, and while he said it wouldn’t be a distraction, the longer his future is unresolved, surely it will be in the back of his mind.

We had a sneak-peak in 2016-2017 with Wilshere playing on-loan at Bournemouth. Perhaps next season we’ll see Wilshere playing away from the Arsenal colors again. This time, on a permanent basis, unless Wenger changes his mind.

Bolt to train with Borussia Dortmund on Friday

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DORTMUND, Germany (AP) Sprint star Usain Bolt is set to train with German soccer team Borussia Dortmund on Friday.

The Bundesliga club says the eight-time Olympic champion, whose last race before retirement was at the 2017 world championships, will “participate in an open training session” with coach Peter Stoeger’s side.

Bolt posted a picture of himself in a Dortmund shirt on Twitter, saying, “BVB, get ready for Friday.”

Dortmund, which shares a sponsor with Bolt in sportswear giant Puma, had long said that the 31-year-old could train with the team at some stage.

Dortmund’s next game after the international break is at Bayern Munich on March 31. Bayern can secure the league title then if other results go its way.

Can says he wants to play for “very big club” next year

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Liverpool swing man Emre Can – whose contract expires this summer – has not yet found a club to sign with yet, and the future free agent is playing up his own talents while looking for a new home.

“I have the self-confidence to say that my qualities are sufficient to play in a very big club next season,” Can told German newspaper Suddeutche Zeitung. “I’m doing great in England. The Spanish league is also attractive. The same applies to Germany, where tactics are concerned, and the Italian club football, which has recently caught up.”

“Incidentally, the same applies to France, this league has now established itself as one of the best in Europe. Therefore, I do not want to exclude anything.”

However, Can also said that the Premier League’s spending power plays a major role, and singled out the German top flight – his home country – for its inability to pay top players.

“Sure, the Bundesliga would interest me, why not? Although I must say honestly that the level has waned in recent years,” he said. “The Premier League has the power to spend more money on players than the Bundesliga. This is very, very important for players.”

Despite those comments, the 24-year-old insists that money is not the ultimate deciding factor in where he will play.

“What counts for me is that I’m an integral part of the team and at a club with a chance of winning the title,” he added. “That’s what every footballer dreams of because that’s the reward of your hard work.”

Can has not ruled out a return to Liverpool, a club that he says “still feels like family.”