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

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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.

Loss to Sevilla quickly puts Real Madrid’s Zidane on the defensive

SEVILLE, SPAIN - JANUARY 15:  Head Coach of Real Madrid CF Zinedine Zidane looks on prior to  the match against Real Madrid CF during the La Liga match between Sevilla FC and Real Madrid CF at Estadio Ramon Sanchez Pizjuan on January 15, 2017 in Seville, Spain.  (Photo by Aitor Alcalde/Getty Images)
Photo by Aitor Alcalde/Getty Images
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MADRID (AP) Real Madrid’s first loss after a 40-game unbeaten streak was enough to put coach Zinedine Zidane on the defensive.

Two days after Madrid’s unbeaten record was halted by a 2-1 defeat at Sevilla in the Spanish league, Zidane was forced to defend some of his players against criticism from fans and local media.

[ MORE: Klopp, Liverpool still consulting lawyers over absurd Matip situation ]

Most comments were aimed at goalkeeper Keylor Navas, who failed to stop Sevilla’s injury-time winner on Sunday. Navas got to Stevan Jovetic‘s long-range shot but was unable to keep the ball from going in.

“He’s having a really good season,” Zidane said on Tuesday. “You can always ask for more, but if up until now we had gone 40 games without losing, it’s for a reason, and he has been there all the way.”

There have been calls for Zidane to give reserve goalkeeper Kiko Casilla a chance, but the coach said there was “no need to go over this again.”

Zidane also dismissed talk about signing a new goalkeeper.

“These are rumors,” he said. “We are focused on what we are doing this year. Whatever happens next I’m not interested and it’s not the time to talk about it. The three goalkeepers we have are important, they’re doing well and I’m very happy with them. I don’t want to change anything we’re doing.”

[ MORE: How Sevilla hope to break up the Madrid-Barca duopoly ]

Zidane defended forward Karim Benzema, who lost possession near midfield in a mistake that led to host Sevilla’s winner on Sunday.

“Everyone can say and write what they want,” Zidane said. “On a field, playing 90 minutes, you can’t do everything right. There is talk of lack of concentration, but we only had five bad minutes and that happens in football.”

Benzema also missed a chance to score from close range in the game, but a few days earlier it was the French striker who netted in stoppage time in a Copa del Rey match against Sevilla to help Madrid set the Spanish unbeaten record.

Zidane downplayed the end of Madrid’s unbeaten streak. The club hadn’t lost since a 2-0 defeat at Wolfsburg in the Champions League in April.

[ MORE: Monday’s transfer rumor roundup | Sunday | Friday | Thursday ]

“These things happen,” he said. “Nothing is going to change in what I’m going to do. Those who are not Real Madrid fans will want us to lose, but we must be ready and think that what we’re doing is fine. We lost a game, something that happens, and now we have to make sure that it doesn’t happen again.”

Madrid hosts Celta Vigo on Wednesday in a first-leg match in the quarterfinals of the Copa del Rey.

Celta has won all four matches this year.

“I am not surprised by Celta’s record because they’re a very good team, they fight and play very good football,” Zidane said. “It’ll be another complicated match for us.”

FA fines Man City’s Sagna over “10 against 12” Instagram message

MANCHESTER, ENGLAND - JANUARY 02: Scott Arfield of Burnley (L) tackles Bacary Sagna of Manchester City (R) during the Premier League match between Manchester City and Burnley at Etihad Stadium on January 2, 2017 in Manchester, England.  (Photo by Shaun Botterill/Getty Images)
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LONDON (AP) The English Football Association has fined Manchester City defender Bacary Sagna 40,000 pounds (around $50,000) for an Instagram post about a referee.

[ FOLLOW: All of PST’s PL coverage ]

Sagna posted a photo with the caption “10 against 12.. but still fighting and winning as a team” on the social network site following City’s 2-1 win against Burnley on Jan. 2.

Sagna later amended the post to read “still fighting and winning as a team” after a match that saw referee Lee Mason send off midfielder Fernandinho.

[ MORE: Klopp, Liverpool still consulting lawyers over absurd Matip situation ]

The FA also warned Sagna about his future conduct.

Klopp, Liverpool still consulting lawyers over in-limbo Matip

LIVERPOOL, ENGLAND - DECEMBER 11: Joel Matip of Liverpool and Andre Ayew of West Ham United compete for the ball during the Premier League match between Liverpool and West Ham United at Anfield on December 11, 2016 in Liverpool, England.  (Photo by Jan Kruger/Getty Images)
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Few footballing sagas will ever reach heights of absurdity comparable to that of the Joel Matip/Liverpool versus Cameroon/FIFA battle currently raging, as the Reds defender finds himself “ineligible” to play for his club due to an international call-up 18 months after announcing his international retirement.

[ FOLLOW: All of PST’s PL coverage ]

PST’s Joe Prince-Wright summed up the situation quite well, in full, right here. An excerpt:

Matip, 25, was called up by the Cameroon national team for the 2017 African Cup of Nations which is currently taking place in Gabon. However, the former Schalke defender has previously stated that he did not want to play for them and he had retired from international duty.

Cameroon called him into their initial 35-man squad for the competition anyway but did not include him in their final 23-man squad once it became clear Matip, along with six other players, had no interest in playing for them at AFCON.

FIFA has confirmed that Liverpool has been in touch regarding Matip’s status and it now appears that he will not be able to play in any other competition while Cameroon is still in AFCON action under Article 5 of FIFA’s rules.

[ MORE: Monday’s transfer rumor roundup | Sunday | Friday | Thursday ]

Fast forward a few days, and Jurgen Klopp and Co. have no further clarity regarding the situation. It’s so unclear, in fact, that Klopp said on Tuesday he may select the 25-year-old during one of two remaining games this week, and hope for the best — quotes from the Guardian:

“As you can imagine, we are in a lot of talks. We’ve done transfers quicker than this. It’s already long term but now it’s getting really tense on our side. We’ve tried everything but at the end I have to make the decision. Of course I have to ask [Liverpool’s lawyers] but the decision is for me to make. I could put him in the lineup. I don’t think the referee is going to say: ‘Stop, stop, you cannot go on the pitch.’ But I will do it when it’s OK from our point of view. Of course I need advice — I’m not a lawyer.”

“Most of the time in life you know if you do this, then you get this. But it’s not 100 percent clear what happens [if Matip plays]. We try everything to win football games. If this can happen — out of the tournament or whatever — then we have to decide about the risk. He’s ready to play for us and that makes it difficult.”

What an utter disaster of a situation Cameroon have intentionally created here.

VIDEO: Jeison Murillo’s incredible bicycle from a corner kick

MILAN, ITALY - JANUARY 17:  (R-L) Jeison Murillo of FC Internazionale celebrates his first goal with Geoffrey Kondogbia during the TIM Cup match between FC Internazionale and Bologna FC at Stadio Giuseppe Meazza on January 17, 2017 in Milan, Italy.  (Photo by Pier Marco Tacca/Getty Images)
Photo by Pier Marco Tacca/Getty Images)
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Look away now, Andy Carroll. Take a bow, Jeison Murillo.

[ VIDEOS: All in a week’s work — Messi free kick no. 1 | Messi free kick no. 2 ]

Just three days after Carroll scored the bicycle-kick goal of the year (so we thought), here comes Murillo, Inter Milan’s 24-year-old Colombian striker, to steal his thunder (below video). The fact he did it directly from a corner kick, with the ball traveling roughly 40 yards before flinging his body into the air and striking the ball so cleanly, (somehow) trumps Carroll’s accomplishment from Saturday.

[ MORE: PL Power Rankings — Tight at the top… and bottom ]

Sensational goals come in twos now, apparently, as Henrikh Mkhitaryan and Olivier Giroud scored stunning scorpion-kick goals (WATCH HERE and HERE) just days apart earlier in the season.