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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.

Premier League roundup: Top Four has separation; Relegation picture much clearer

SUNDERLAND, ENGLAND - FEBRUARY 13: Louis van Gaal Manager of Manchester United looks on prior to the Barclays Premier League match between Sunderland and Manchester United at the Stadium of Light on February 13, 2016 in Sunderland, England.  (Photo by Clive Brunskill/Getty Images)
Photo by Clive Brunskill/Getty Images
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A couple of lessons from Saturday in the Premier League:

  1. The reasonable relegation field has slimmed
  2. Thanks to two other sides, so has the Top Four

Manchester United and West Ham United both stumbled in a quest to make up ground on the top four sides in the Premier League, who face off with each other on Sunday.

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And Norwich City’s point coupled with Chelsea’s demolition of Newcastle United has the contestants for the Bottom Three looking pared down to six clubs.

Sunderland 2-1 Manchester UnitedRECAP

United will finish the weekend a minimum of six points outside of the Top Four after allowing a third minute goal and another about the same distance from the final whistle in its first ever loss at the Stadium of Light. Wahbi Khazri looks the part for Sunderland, who moved to within a point of safety with the win. Anthony Martial scored for United

Swansea City 0-1 SouthamptonRECAP

Fraser Forster has six-straight shutouts and Saints are knocking on the door of fifth place after picking up three points in Wales. Shane Long‘s late goal lifted Saints to the win and 40 points on the season, while Swans are three points ahead of 17th place Norwich City and 18th place Newcastle.

during the Barclays Premier League match between Chelsea and Newcastle United at Stamford Bridge on February 13, 2016 in London, England.

Chelsea 5-1 Newcastle UnitedRECAP

Newcastle started a makeshift back four with winger Rolando Aarons filling in at fullback, and Chelsea absolutely devoured the Magpies to win its first season series against the Northeast side since 2011. Pedro nabbed a pair of goals, with Bertrand Traore adding his first Premier League goal. Diego Costa and Willian also scored, and Andros Townsend added his first goal since leaving Spurs in the January transfer window. Newcastle is 18th after the blowout loss sunk them beneath Norwich on differential.

Norwich City 2-2 West Ham UnitedRECAP

And that’s because the Canaries tossed away a 2-0 home lead against Dimitri Payet. We should say West Ham, but Payet has been an absolute wizard for the Irons and scored before setting Mark Noble up for a second in erasing the deficit caused by goals from Robbie Brady and Wes Hoolahan. For the moment, Norwich is 17th and the Hammers failed in a bid to overtake Manchester United for fifth.

BOURNEMOUTH, ENGLAND - FEBRUARY 13: Giannelli Imbula of Stoke City controls the ball under pressure of Harry Arter of Bournemouth  during the Barclays Premier League match between A.F.C. Bournemouth and Stoke City at Vitality Stadium on February 13, 2016 in Bournemouth, England.  (Photo by Paul Gilham/Getty Images)
BOURNEMOUTH, ENGLAND – FEBRUARY 13: Giannelli Imbula of Stoke City and Harry Arter of Bournemouth  (Photo by Paul Gilham/Getty Images)

Bournemouth 1-3 Stoke CityRECAP

Giannlli Imbula, Joselu and Ibrahim Afellay helped the Potters cruise to a win at Vitality Stadium, halting its slide while moving Bournemouth smack dab back in the relegation frame. The Cherries are four points free of the drop zone, and Matt Ritchie‘s goal was part of a game comeback effort from Eddie Howe‘s bunch.

Everton 0-1 West Bromwich Albion — RECAP

The Toffees managed an incredible 34 shots, but couldn’t slip one past a packed-in West Brom side. The Baggies closed up shop after Salomon Rondon scored in the 14th minute, West Brom’s only shot on target of the night. Tony Pulis‘ side is eight points clear of the drop.

Crystal Palace 1-2 WatfordRECAP

Alan Pardew‘s Eagles are all the way down to 13th and winless in 2016 Premier League matches. With just one point from its last seven matches, Palace needs a win soon to avoid being a very real part of the relegation picture. Quique Flores‘ Hornets, however, are essentially safe after moving to within five points of fifth. Troy Deeney scored both of Watford’s goals, while Emmanuel Adebayor netted for Palace.

 

Standings

Team GP W D L GF GA GD Home Away PTS
Leicester City 25 15 8 2 47 27 20 7-4-1 8-4-1 53
Tottenham Hotspur 25 13 9 3 45 19 26 7-4-2 6-5-1 48
Arsenal 25 14 6 5 39 22 17 7-3-2 7-3-3 48
Manchester City 25 14 5 6 47 26 21 9-1-3 5-4-3 47
Manchester United 26 11 8 7 33 24 9 6-4-2 5-4-5 41
Southampton 26 11 7 8 34 24 10 7-2-4 4-5-4 40
West Ham United 26 10 10 6 40 31 9 5-5-2 5-5-4 40
Watford 26 10 6 10 29 28 1 5-3-5 5-3-5 36
Stoke City 26 10 6 10 27 32 -5 5-2-5 5-4-5 36
Everton 26 8 11 7 46 35 11 4-4-6 4-7-1 35
Liverpool 25 9 8 8 32 36 -4 4-5-3 5-3-5 35
Chelsea 26 8 9 9 38 36 2 5-5-4 3-4-5 33
Crystal Palace 26 9 5 12 27 32 -5 4-2-8 5-3-4 32
West Bromwich Albion 26 8 8 10 24 32 -8 4-4-5 4-4-5 32
Bournemouth 26 7 7 12 30 44 -14 3-4-6 4-3-6 28
Swansea City 26 6 9 11 24 34 -10 4-5-5 2-4-6 27
Norwich City 26 6 6 14 30 50 -20 4-4-5 2-2-9 24

Newcastle United 26 6 6 14 27 49 -22 4-5-4 2-1-10 24
Sunderland 26 6 5 15 32 50 -18 4-3-6 2-2-9 23
Aston Villa 25 3 7 15 20 40 -20 2-4-6 1-3-9 16

Watch Live: USWNT takes on Mexico in Olympic qualifier no. 2

Costa Rica defender Carol Sanchez, left, helps goalie Dinnia Diaz (1) on a shot by U.S.forward Alex Morgan, center, during the second half of a CONCACAF Olympic qualifying tournament soccer match Wednesday, Feb. 10, 2016, in Frisco, Texas. Morgan scored 12 seconds in and added another goal in the 62nd minute. The United States won 5-0.. (AP Photo/Tony Gutierrez)
AP Photo/Tony Gutierrez
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The latest chapter in the United States versus Mexico soccer rivalry takes place on Saturday, as the United States women’s national team faces the Mexican women’s national team in the second game of 2016 Olympic qualifying.

The game, which kicks off at 4 p.m. ET, can be seen live on NBC Sports Live Extra (link below) from Toyota Stadium in Frisco, Tex.

[ WATCH LIVE: USWNT vs. Mexico live online on NBC Sports Live Extra ]

Mexico currently sits atop Group A after a 6-0 drubbing of Puerto Rico in their opening game, while the USWNT are a very close second, having beaten Costa Rica 5-0 on Wednesday.

Injury update: Hiddink not hopeful Terry will face PSG this week

Chelsea's captain John Terry stands dejected after being defeated by Newcastle United at the end of their English Premier League soccer match at St James' Park, Newcastle, England, Saturday, Dec. 6, 2014. (AP Photo/Scott Heppell)
AP Photo/Scott Heppell
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John Terry‘s Chelsea future is already very much in peril, and now the 35-year-old, 18-year servant of the club’s final foray into the UEFA Champions League is in just as much doubt.

[ FOLLOW: All of PST’s PL coverage ]

Terry left Saturday’s 5-1 victory over Newcastle United after just 38 minutes, shortly after picking up a hamstring injury in a nasty collision with and landing alongside Aleksandar Mitrovic. After the game, interim Chelsea manager gave a brief update on Terry’s status and subsequent availability for Tuesday’s Champions League clash with Ligue 1 giants Paris Saint-Germain — quotes from the BBC:

“We have just two days to recover and it is something to think about in the future because two days of recovery is not enough.”

Chelsea boss Guus Hiddink says they will know what John Terry’s injury situation is tomorrow. Doesn’t sound hopeful of him facing Paris St-Germain on Tuesday (but didn’t rule it out).

Terry will undergo a scan on his hamstring, which will determine the severity of injury and the time he is to miss, on Sunday.

Chelsea are already without defender Kurt Zouma, who suffered a nasty knee injury last weekend. Couple that with Terry’s injury on Saturday, and 20-year-old American center back Matt Miazga is now an injury to or sending-off of Gary Cahill or Branislav Ivanovic away from making his Chelsea debut in the Champions League and/or Premier League.

Chelsea 5-1 Newcastle United: Blues cruise past hapless Magpies

during the Barclays Premier League match between Chelsea and Newcastle United at Stamford Bridge on February 13, 2016 in London, England.
Photo by Clive Mason/Getty Images
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  • Costa opens scoring in fifth minute
  • His 8th goal in 10 appearances
  • Magpies back into drop zone on goal diff.
  • Townsend strikes late to break shutout

Diego Costa and Pedro scored before the match was nine minutes old, and Willian put an exclamation point on a wild first half in the 17th minute as Chelsea battered Newcastle United at Stamford Bridge on Saturday.

Pedro added another in the second half before Bertrand Traore tallied his first Premier League goal to make it 5-0. Chelsea now has 33 points, and is within two points of 10th and nine back of fifth place Manchester United.

Newcastle is back in 18th, lower than Norwich City on goal differential. Andros Townsend scored late for the Magpies.

[ MORE: Watch full PL match replays ]

It took barely more than four minutes for Chelsea to take the lead, as Costa burst past Steven Taylor to slide Willian’s pass past Rob Elliot. 1-0.

Pedro doubled the advantage when he took advantage of 20-year-old Rolando Aarons, who was forced to play right back despite starting as a right wing under Alan Pardew. It was an awful pass regardless of his normal position, and Pedro picked it off and went the distance.

Andros Townsend cut in from the left to provide a counter threat, but his low shot was gobbled up by Thibaut Courtois.

Still, 3-0 came first. Costa worked a long ball and then watched Fabricio Coloccini back off. Willian tore through an unmarking back line to push home an easy goal.

[ MORE: Latest Premier League standings ]

[ MORE: Full lineups, stats, box score ]

The Magpies found some life in the second half, as Chelsea had to cope with an injury to John Terry that moved Branislav Ivanovic inside and put Baba Rahman into the game.

Aleksandar Mitrovic absorbed a tricky cleat to his achilles, staying in the game to hit a low shot wide of goal.

But Pedro added another goal moments later on a counterattack (of sorts) and it was 4-0 in the 59th minute.

Townsend broke the shutout when he belted a left footed shot home late for his first ever Newcastle goal.