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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.

MLS Preview: Conference leaders meet as Philly head west to Colorado

COMMERCE CITY, COLORADO - APRIL 02:  Dillon Powers #8 of Colorado Rapids controls the ball against the Toronto FC at Dick's Sporting Goods Park on April 2, 2016 in Commerce City, Colorado. The Rapids defeated Toronto FC 1-0.  (Photo by Doug Pensinger/Getty Images)
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The weekend is nearing, which means another full slate of ten matches across Major League Soccer.

[ FOLLOW: All of PST’s MLS coverage ]

With Sporting KC and D.C. United kicking things off on Friday night, Saturday is jam-packed with eight matches before the league’s youngest clubs NYCFC and Orlando wrap up the action on Sunday.

Colorado Rapids vs. Philadelphia Union — Saturday, 9:00 p.m. ET

There’s not a misprint on the table, Colorado and Philadelphia are both at the top of their conferences. After sitting near the bottom of MLS for the past two seasons, Colorado has shocked everyone, currently leading the league in points (27) with the fewest goals conceded (9). On Saturday, the Rapids put their perfect 6-0 home record on the line when they host the Union, who currently lead the East by two points.

New York Red Bulls vs. Toronto FC — Saturday, 7:00 p.m. ET

Coming off of a massive 7-0 win in the Hudson River Derby against NYCFC, the Red Bulls will look to continue trending upwards when they host Toronto FC. Two of the preseason favorites to top the Eastern Conference, both sides are currently tied on points, although the Red Bulls have a game in hand. For Toronto, Sebastian Giovinco will be keen to prove Antonio Conte wrong after being left out of the Italy squad for EURO 2016 after the Italian boss talked down upon MLS.

[ MLS: Standings | Stats | Schedule ]

Montreal Impact vs. Los Angeles Galaxy — Saturday, 8:00 p.m. ET

Didier Drogba has scored in each of his last three starts, a streak he will look to keep alive against the Los Angeles Galaxy this weekend. While Drogba will be looking to score, Montreal must make sure their defense is in top form as the Galaxy have scored a league-high 25 goals through 11 matches.

Elsewhere around MLS

Sporting KC vs. D.C. United — Friday, 7:00 p.m. ET
Vancouver Whitecaps vs. Houston Dynamo — Saturday, 6:00 p.m. ET
Columbus Crew SC vs. Real Salt Lake — Saturday, 7:30 p.m. ET
New England Revolution vs. Seattle Sounders — Saturday, 7:30 p.m. ET
Chicago Fire vs. Portland Timbers — Saturday, 8:30 p.m. ET
San Jose Earthquakes vs. FC Dallas — Saturday, 10:30 p.m. ET
New York City FC vs. Orlando City SC — Sunday, 4:30 p.m. ET

Cantona claims ethnicity played role in Benzema, Ben Arfa France snubs

SHANGHAI, CHINA - APRIL 14:  Former Footballer Eric Cantona of France speaks during a press conference at the Shanghai Grand Theatre prior to the  Laureus World Sports Awards  on April 14, 2015 in Shanghai, China.  (Photo by Ian Walton/Getty Images for Laureus)
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Eric Cantona has made the headlines again, this time making some bold claims against France national team manager Didier Deschamps.

Cantona, a former Manchester United legend and French international, questioned whether Deschamps excluded Karim Benzema and Hatem Ben Arfa from the team due to their North African origins.

[ MORE: Skrtel set to leave Liverpool ]

Speaking to The Guardian, Cantona calls Benzema and Ben Arfa two of France’s best footballers, both of whom will not be playing for the national team this summer.

Benzema is a great player. Ben Arfa is a great player. But Deschamps, he has a really French name. Maybe he is the only one in France to have a truly French name. Nobody in his family mixed with anybody, you know.

So I’m not surprised he used the situation of Benzema not to take him. Especially after [French Prime Minister Manuel Valls] said he should not play for France. And Ben Arfa is maybe the best player in France today. But they have some origins. I am allowed to think about that.

One thing is for sure – Benzema and Ben Arfa are two of the best players in France and will not play the European Championship. And for sure, Benzema and Ben Arfa, their origins are north African. So, the debate is open.

Cantona’s view doesn’t hold much merit as Deschamps did not even have the option of selecting Benzema, the country’s active leading goalscorer. The Real Madrid striker is suspended by the federation, embroiled in a blackmail sex-tape scandal involving French teammate Mathieu Valbuena, who was also left off the EURO roster.

[ MORE: Three battles that could determine the Champions League final ]

France is an extremely diverse nation with a large North African population, Benzema of Algerian descent and Ben Arfa’s father a former Tunisian international. Both players were born in France and have received prior call-ups under Deschamps, with Cantona’s quite ridiculous comments likely to cause a stir before the EURO.

FA Cup will no longer have quarterfinal replays

HALIFAX, ENGLAND - NOVEMBER 09:  The FA Cup is seen prior to the FA Cup First Round match between FC Halifax and Bradford City  on November 9, 2014 in Halifax, England.  (Photo by Clive Rose/Getty Images)
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Starting in 2017, the FA Cup will no longer have replays in the quarterfinal round.

The decision was made in an effort to combat the congested English fixture list, which has been a topic of debate for years now.

[ MORE: Lukaku wants out at Everton ]

This season, Manchester United defeated West Ham in a quarterfinal replay before going on to win the competition.

In a statement released by the FA, these changes aim to add drama to the matches while eliminating an extra matchday needed for replays.

The revamped competition will see eight clubs battle it out over one weekend with each tie to be played to a finish on the day, adding to the drama and impact the competition has enjoyed in recent years.

Other new initiatives will be explored to ensure The FA Cup retains its status and appeal. These plans also form part of The FA’s commitment to help ease English football’s congested fixture schedule.

There will still be replays in the earlier rounds of the tournament, which allows lower level clubs the opportunity to earn a nice financial boost should they force a second match at a Premier League ground.

The Premier League is the only top league in Europe that does not take a winter break, a schedule that has been criticized by multiple managers, including Jurgen Klopp.

Judge hears arguments on US women’s team strike rights

HARRISON, NJ - MAY 30:  The United States team poses for a team picture before the match against the South Korea during an international friendly match at Red Bull Arena on May 30, 2015 in Harrison, New Jersey.  (Photo by Elsa/Getty Images)
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CHICAGO — A federal judge in Chicago has heard arguments whether the world champion U.S. women’s soccer team has the right to strike for improved conditions and wages before this year’s Olympics.

Lawyers for the U.S. Soccer Federation told Judge Sharon Johnson Coleman at a Thursday hearing that a no-strike clause is implied in a still-valid 2013 memorandum with players.

[ MORE: All of PST’s USWNT coverage ]

But a lawyer for the U.S. Women’s National Soccer Team Players Association balked at that claim. Jeffrey Kessler said the federation had “screwed up” by not securing a no-strike clause in writing and can’t argue three years later that such a provision is implied.

The union wants the option to strike before the Olympics start in August, but hasn’t said it will. Many players have voiced concern over gender equity in soccer.