Barcelona's midfielder Xavi Hernandez re

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.

MLS Cup Playoffs: NY Red Bulls 1-0 (1-2 agg.) Columbus Crew SC

Tony Tchani, Michael Parkhurst

The game in 100 words (or less): Columbus Crew SC are headed to their second MLS Cup in club history (champions – 2008) after defeating the New York Red Bulls, 2-0 on aggregate, in the Western Conference finals (0-0 draw in an extremely chippy second leg on Sunday). Justin Meram and Kei Kamara scored the two-leg tie’s only goals — eight seconds and 85 minutes into the first leg, respectively — and Crew SC confidently managed the second leg by defending with numbers and wisely picking their spots to break out on the counter. RBNY held nearly 60 percent of possession in the second leg, but could muster just six shots on target over the 90 minutes. Crew SC will host the Portland Timbers in MLS Cup 2015 next Sunday (4 p.m. ET) at MAPFRE Stadium.

[ MORE: Previewing the MLS weekend ]

Three moments that mattered

38′ — Robles at full stretch to deny Kamara — What’s better: the first touch, second touch, turn and shot by Kei Kamara; or, the sprawled-out save by Luis Robles to swat away a ball clearly headed for the bottom corner? Quality on quality.

90+3′ — Abang heads home to make it nervy late — Anatole Abange rose above the crowd and headed home a recycled ball inside the penalty area after a Sal Zizzo cross was headed high into the air late into stoppage time.

90+5′ — Madness in the penalty area, RBNY hit the post — It was absolute scenes inside the Crew SC penalty area. Ball after ball pumped into the box, headed high into the air and briefly cleared. The final chance of the game fell to Bradley Wright-Phillips, who headed the ball toward the far post with Steve Clark rushing out quickly, only to see his slow dribbler bounce off the front side of the post and back into the field of play.

[ FOLLOW: All of PST’s MLS coverageStandings | Stats | Schedule ]

Man of the match: Wil Trapp

Goalscorers: Abang (90+3′)

MLS Cup Playoffs: FC Dallas 2-2 (3-5 agg.) Portland Timbers

Fanendo Adi, Portland Timbers FC
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The game in 100 words (or less): The Portland Timbers are headed to their first MLS Cup in club history after defeating FC Dallas, 5-3 on aggregate, in the Western Conference finals (2-2 draw in the second leg). Fanendo Adi scored in Sunday’s second leg, giving Caleb Porter’s side a 4-1 aggregate lead before Ryan Hollingshead and Blas Perez scored inside the last 25 minutes to give Oscar Pareja’s bunch a late lifeline, but Lucas Melano’s spectacular tap-in sealed the Timbers’ trip to MLS Cup. The third seed heading into the playoffs, Portland bounced Sporting Kansas City in an epic penalty shootout in the knockout round and outlasted the Vancouver Whitecaps in the conference semifinals before knocking off the West’s top seed over two legs to advance to MLS Cup 2015. No matter who advances from the East finals later on Sunday, Portland will play away in MLS Cup, to either the New York Red Bulls or Columbus Crew SC.

[ MORE: Previewing the MLS weekend ]

Three Four moments that mattered

54′ — Adi fires past Gonzalez to make if 4-1 — Oscar Pareja elected to go with Walker Zimmerman at center back on Sunday, dropping regular starter Zach Loyd to the bench. On the game’s opening goal, it was Zimmerman who wound up on the ground as Adi received the ball, turned and fired a massive away goal past Jesse Gonzalez.

68′ — Diaz’s magical ball curled home by Hollingshead — Mauro Diaz is a wonderful magician capable of playing the kill through ball from anywhere on the field — this we’ve known for quite some time. His chipped through ball to set up Hollingshead’s goal was extraordinarily brilliant, even for him.

73′ — Perez heads home the free kick to pull within one — Would you be surprised to hear that it was Diaz who set up FCD’s second goal? His free kick was Perez-finding missile and found the head of the Panamanian striker at the top of the six-yard box, where 34-year-old headed home with ease.

90+5′ — Melano rounds Gonzalez, seals MLS Cup berth — Poor Jesse Gonzalez. Absolutely schooled and posterized by Lucas Melano. What a way to sew up a place in the championship final.

[ FOLLOW: All of PST’s MLS coverageStandings | Stats | Schedule ]

Man of the match: Mauro Diaz

Goalscorers: Adi (54′), Hollingshead (68′), Perez (73′), Melano (90+5′)

La Liga & Serie A: Real Madrid bounce back; Juventus on the charge

Gareth Bale, Real Madrid CF
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A roundup of all of Sunday’s action in Spain and Italy’s top flights:

Eibar 0-2 Real Madrid

Real Madrid bounced back from back-to-back La Liga defeats with a 2-0 victory away to Eibar on Sunday. Gareth Bale (below video) and Cristiano Ronaldo (penalty kick) provided the goals to keep Rafa Benitez‘s bunch (27 points) third in the league, two points behind Atletico Madrid and six behind leaders Barcelona.

Elsewhere in La Liga

Getafe 2-0 Villarreal
Rayo Vallecano 0-3 Athletic Bilbao
Sevilla 1-0 Valencia

[ MORE: Saturday’s La Liga roundup ]

Roma 0-2 Atalanta

Losing at home to sides currently in a relegation battle — rarely a good idea, especially if you fancy yourselves title challengers, but that didn’t stop Roma from doing just that on Sunday. Alejandro Gomez and German Denis scored the goals to knock off a 10-man Roma side (Maicon – 81st minute) and keep Rudi Garcia’s bunch (27 points) from gaining ground on any of the three teams currently ahead of them — Inter Milan, Napoli and Fiorentina — all of whom play on Monday.

AC Milan 4-1 Sampdoria

M’Baye Niang scored twice, while Giacomo Bonaventura and Luiz Adriano (below video) added single tallies for AC Milan (23 points) to keep pace with the top-five pack in Serie A. After 14 rounds of games, the Rossoneri sit sixth, a point outside fifth (UEFA Europa League) and five points out of third (UEFA Champions League).

Palermo 0-3 Juventus

Don’t look now, but here come Juventus. Sunday’s 3-0 triumph over Palermo makes it four straight wins in the league for Massimiliano Allegri’s side — a run that pushes them all the way up to fifth in the league (24 points), just six points off the pace of leaders Inter, who play on Monday. Mario Mandzukic (below video), Stefano Sturaro and Simone Zaza scored the goals for the world’s most frightening fifth-place team.

Elsewhere in Serie A

Torino 2-0 Bologna
Chievo 2-3 Udinese
Frosinone 3-2 Hellas Verona
Genoa 1-2 Carpi
Empoli 1-0 Lazio

Monday’s Serie A schedule

Sassuolo vs. Fiorentina (1 p.m. ET)
Napoli vs. Inter Milan (3 p.m. ET)

Arsenal’s injury crisis — add Sanchez, Cazorla, Koscielny to the list

Alexis Sanchez, Arsenal FC
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From title challengers to just hoping to hold on to a top-four place while Arsene Wenger is forced to play reserves and academy players because half of his star players are currently out injured — the annual story of Arsenal.

[ FOLLOW: All of PST’s PL coverage ]

Oct. 27, when Theo Walcott and Alex Oxlade-Chamberlain both went down with injuries in the same game, marked the unofficial start of Arsenal’s 2015-16 injury crisis, but things didn’t really get going full bore until the last seven days, when five more players — four of them full-time starters — picked up injuries that will keep them out of action for anywhere between three weeks and three months.

Added to the list last weekend: Francis Coquelin (knee – three months minimum), Mikel Arteta (calf – three weeks)

Added to the list on Sunday: Alexis Sanchez (hamstring – MORE DETAILS), Santi Cazorla (knee), Laurent Koscielny (hip)

Following Sunday’s 1-1 draw with Norwich City, Wenger said Koscielny “could not walk” due to the hip spasm that forced him out of the game after just 11 minutes. He also divulged that Cazorla, who could not be subbed off because Wenger had already used all three subs late on, played the second half “on one leg.” Sanchez came into Sunday injured after picking up a hamstring injury in Arsenal’s UEFA Champions League victory over Dinamo Zagreb on Tuesday.

[ MORE: Sunday’s PL roundup — Chelsea, Arsenal, Spurs all draw ]

Arsenal fans were up in arms during the summer transfer window — let’s be honest, the following is true of every transfer window the last five years — crying out, “We must buy, we must buy.” Have a look at Arsenal’s complete injury list at the moment, and try to say, “They didn’t need to buy in the summer.”

In chronological order: Danny Welbeck (knee – early 2016 return), Tomas Rosicky (knee – Christmas time return), Jack Wilshere (leg – Christmas time return), Theo Walcott (calf – December return), Mikel Arteta (calf – three weeks), Francis Coquelin (knee – three months minimum), Laurent Koscielny (hip – to be assessed), Alexis Sanchez (hamstring – to be assessed), Santi Cazorla (knee – to be assessed)