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.

Fan protests spur Fiorentina owners to put club up for sale

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FLORENCE, Italy (AP) The owners of two-time Serie A champion Fiorentina have announced they are putting the club up for sale due to fan protests.

A club statement says the ownership is accepting “serious offers only from those who really mean well for the Viola shirt.”

Shoe and leather entrepreneurs Diego and Andrea Della Valle have controlled Fiorentina since 2002, having restarted the club after the previous ownership ended in bankruptcy.

The Della Valles guided the club up from the fourth division back to the top flight but were never fully embraced by the squad’s fans.

After four straight years of finishing in the top five of Serie A, an eighth-place result last month was difficult to accept by the supporters.

Former Fiorentina captain Stefano Pioli was recently appointed to coach the club.

De Boer an exciting hire for “club that can grow further and further”

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Frank De Boer said all the right things in his first interview as Crystal Palace boss, and Eagles fans should puff out their chests at the club’s most impressive hire in a long time.

On the heels of blustery Sam Allardyce, Alan Pardew, and to a much lesser extent Tony Pulis, De Boer is no shrinking violet.

Yet the Dutchman has set the standards high for his London debut. There’s no talk of “just surviving” or whimpering at the might of the league’s top clubs. De Boer’s ready to do well.

[ MORE: Ranking expectations for PL bosses ]

Appointed Monday, De Boer will take charge of his third club following stints at Ajax and Inter Milan. He won four titles in five season at the Dutch club, but spent just 85 days in that tumultuous seat.

From CPFC.co.uk:

“It’s a club that can grow further and further because English clubs in the Premier League can spend a lot of money, and we can do something well with that. There is the prospect to be a solid Premier League club and this is the most important thing for me right now, not struggle for relegation. If we can do more that would be nice, but we want to be a stable club.”

Palace chairman Steve Parish has taken a solid step in the hiring of De Boer, who becomes just the second Palace boss from outside the British Isles. He’ll have an array of attacking options, but will probably need to look past his current batch of defenders to find players who fit his style.

That said, he’s said he’ll look at his current group first. He’ll love Patrick Van Aanholt and perhaps Jeff Schlupp, but De Boer needs some help at the back. Still, like Mauricio Pellegrino at Saints, this seems like another hire that was worth the wait for a PL fan base.

Still, Palace views itself as a club that can excite, and Allardyce was not the man to set Wilfried Zaha and Andros Townsend up to succeed. In fact, the Eagles have probably been blessed by Allardyce’s retirement, and Parish did not drop the ball when given the opportunity.

Chicharito injury update ahead of Confed Cup semifinals

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KAZAN, Russia (AP) Mexico star Javier “Chicharito” Hernandez trained separately from his teammates on Monday because of muscle fatigue, the latest concern for a Mexican team that has been struck by injuries at the Confederations Cup.

[ MORE: Latest Confed Cup news

Defender Diego Reyes also didn’t practice with the team in its final training session before traveling to Sochi for Thursday’s semifinal against Germany.

Mexico had already lost defender Carlos Salcedo because of a shoulder injury, while defender Hector Moreno has been a concern with a muscle ailment.

Coach Juan Carlos Osorio is already certain to be without midfielder Andres Guardado because of a yellow card suspension.

Chicharito warmed up with the rest of the group in Monday’s practice session in Kazan but left the field after the players met for a few minutes with coach Juan Carlos Osorio.

When one of Osorio’s assistants asked Chicharito about his condition, the player said he was “fine, not a problem.”

The Bayer Leverkusen forward ran a few laps around the field accompanied by the team’s physical trainer, then underwent a few stretching exercises on the sidelines. He watched the rest of the training session from the bench.

The team said Chicharito’s absence was a precaution.

“He said that he was leaving because he was still a bit tired after the match,” midfielder Jonathan Dos Santos said. “He’s played a lot of matches, a lot of minutes, a lot of practices. He just needs to rest a bit, nothing important.”

Chicharito played the entire game when Mexico came from behind to defeat host Russia 2-1 on Saturday to guarantee its spot in the semifinals of the eight-nation World Cup warm-up event.

He was rested in the 2-1 win over New Zealand, when Osorio rotated his squad because of a concern over injuries. Salcedo sustained his shoulder injury during that game and was forced to be removed from the squad. Reyes was hurt in the game against Russia and remains doubtful for the semifinal. He stayed at the team’s hotel on Monday, undergoing rehab for his muscle injury.

Chicharito scored his only goal of the tournament in the 2-2 opening draw against Portugal last week.

Guardado was shown his second yellow against Russia.

“He is a crucial player for us, very important for the team, one of our captains,” Dos Santos said about Guardado. “But we have other players who can make up for his absence.”

Mexico is trying to win the Confederations Cup for the second time. It won the World Cup warm-up event in 1999.

Tales Azzoni on Twitter: http://twitter.com/tazzoni

More AP Confederations Cup coverage: http://www.apnews.com/tag/ConfederationsCup

VIDEO: Fans of Mexican teams brawl in “friendly game”

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This was clearly not a friendly game.

And that was just in the stands.

A game to benefit the United Soccer Talents Foundation was abandoned at half time as fans took to the pitch and brawled in Santa Ana, California.

The “friendly” game was played between former members of rival clubs Club America and Pumas at Eddie West Field as fans of the Mexico City clubs converged.

At half time those fans fought in the stands and then ran onto the pitch to exchange punches as the widespread brawl lasted for 30 minutes, with local law enforcement then arriving to control the situation.

According to NBC LA, five people have been arrested on suspicion of assault and assault with a deadly weapon.

Click play on the video above to see the ugly scenes play out.