How new research on off-ball advantage can help us spot Barça's problem breaking down a low block.
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The good news for Barcelona is they don’t have to score. It took a long, slow slog of a first hour in Naples back in February, an hour in which the erstwhile greatest attack in Europe managed two shots against the seventh-best team in Italy, but Barcelona eventually got their away goal. In this weekend’s return leg they could, theoretically speaking, sit back and defend against Napoli, if sitting back and defending were something Barcelona was even theoretically able to do.
The bad news is that in order to win the Champions League, historical precedent suggests they may need to produce another goal some time between now and the final. Maybe that moment will come after Dries Mertens punishes another ball and then punishes the world with that incredibly upsetting tongue-flicking thing he does for the camera. Maybe it’ll come in the next round. But whenever Barcelona needs to score, odds are it’ll come against an organized low block, and odds are it’ll fall to Lionel Messi to do something about it.
It wasn’t always like this. When Barça has had a left winger to help shoulder the creative load, or a midfield that wasn’t overplaying its hand with three sixes and Arturo Vidal as the wild card, Messi’s done more of his work between the lines, shot more shots inside the box, and been the world’s greatest forward instead of its most reluctant regista. When the game slows down, though—and this season’s Barcelona has had all the zip of continental drift—Messi drops deeper and deeper to speed it up.
When he does, will there be anyone in front of him to pass to?
That’s a question FC Barcelona’s state-of-the-art analytics team has been working on measuring lately. At the 2020 MIT Sloan Analytics Conference, basically the Champions League knockouts for sports nerds, three of the club’s analysts presented research on “off-ball advantage,” using data on all 22 players’ real-time locations to measure when and where they offer valuable passing options that could move a possession forward. The goal, Barça data scientist Pau Madrero told me, was “to evaluate players’ actions not only when they have the ball but also when they are not in possession of the ball and they are trying to help the team.”
Barcelona’s research is based on the latest hot metric in soccer analytics, Expected Possession Value, which measures a team’s likelihood of scoring minus the likelihood of conceding if they turn it over. The EPV model tells you in fractions of goals how much a possession is worth in its current situation. From there you can calculate how much the possession would be worth if the guy on the ball completed a pass to any given teammate, discounted by the likelihood of it successfully getting there. If a teammate is in front of the ball, in enough space to receive, and there’s a viable passing lane to get it to him so that the potential value gain is positive, he’s in an off-ball advantage.
Because Madrero and company work hand in hand with Barça’s tactical analysts, they’re good at presenting their data in a soccer context. The paper breaks off-ball advantage down according to whether it happens in the buildup, progression, or the “finishing phase,” when the team has cracked the defense’s lines and is looking for a goal. It also distinguishes between off-ball advantages occurring inside and outside the opponent’s defensive block.
“It’s difficult by looking at numbers and figures to discover how a team plays, but when you compare it to other teams you see that Barcelona—we already knew, but we verified that they try all the time to play inside the opponent’s block,” Madrero said.
My favorite figure from the paper (which uses data from last season and the first half of this one) compares where Messi and Phillipe Coutinho created off-ball advantages during the progression phase, after Barcelona has beaten the first line of pressure and before they reach the final quarter of the field. Instead of just scattering points all over the field, Barça’s analytics team first plotted dashed lines for the average height of opposing defensive lines and the outer limits of their block, then showed where the off-ball advantages happened in relation to the defense’s structure. It’s a clever viz that lets us see that Messi found space in front of the center backs more often than Coutinho but was also more likely to show for a good pass on the wing.
It seems like a problem for Barcelona that Messi is one of their best players at receiving between the lines—and definitely their most dangerous when he does—but also their only hope for playing that linebreaking pass. (As Gisele once said of Tom Brady, “My husband cannot fucking throw the ball and catch the ball at the same time.”) In the first leg against Napoli, frustrated by Gennaro Gattuso’s 4-5-1 defense that sent Fabián Ruiz and Piotr Zielinski alternately pistoning out of the midfield line to deny passing lanes to Barça’s center backs, Messi kept dropping outside Napoli’s block to receive, then turning at the corner to look for a way back in.
To figure out why he struggled to find that way in, I decided to make my own version of Barcelona’s Sloan viz by hand. That’s not as impossible it sounds, since the off-ball advantage research is really just trying to model the identification of good passing options you ought to be able to see on the field. I counted 22 times that Messi got on the ball facing play in his typical looking-to-break-lines posture: inside the edges of the opponent’s block but in front of its midfield line, almost always on the corner in front of Zielinski and Lorenzo Insigne. Across those 22 times, Messi’s teammates created a total of what looked to me like just 10 really good passing options, what Madrero’s team would call off-ball advantages. Messi found 7 of them. That’s a pretty good hit rate, but Barcelona’s got to do more moving off the ball if they want to play inside the opponent's block.
Sometimes Messi found advantages that didn’t seem to exist, like when he dropped a dime onto Vidal’s forehead over three mystified defenders who'd positioned themselves in a direct line between the pass and the receiver. That might help explain the Barça researchers’ finding that Messi’s real EPV gain was better than the potential EPV gains the model spotted, especially at the high-value end of the spectrum. But not even Messi could find makeshift center forward Antoine Griezmann, who’s never shown the kind of line-stretching movement he’d need to be a viable Luis Suárez replacement. The central area between the lines where Messi likes to receive became, when he dropped to provide, a desolate blank.
And yet Messi dropping to provide was the only way to break through, and it was how Barcelona finally got its goal: a linebreaking pass from Messi to Vidal, who laid off to Busquets, who two-timed a throughball to Semedo, who squared for Griezmann to finish. It was a sensuous move, the kind of vintage coordinated passing and movement the team’s been so conspicuously missing, and it was made possible by Messi’s magnetic field dragging defenders out of their shape, edging a little nearer to him just in case.
It’ll help Barcelona’s scoring prospects on Saturday that Suárez is healthy again, even if his legs get visibly heavier with age every time he steps on the field. It can’t hurt that Riqui Puig spent quarantine blossoming into the closest thing to an Andrés Iniesta-type prospect La Masia has produced since the man himself. But if it comes to crunch time it’ll be down to Messi to drop beyond the defense, demand the ball, and turn to make something happen. We’ll see if anyone shows up to help. ❧
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- Sergio Lana et al., The right place at the right time: Advanced off-ball metrics for exploiting an opponent’s spatial weaknesses in soccer (Sloan 2020)
- Javier Fernández et al., Decomposing the Immeasurable Sport:A deep learning expected possession value framework for soccer (Sloan 2019)
Image: Adrien Dauzats, The Great Pyramid, Giza
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