Four years is a long time. Part of the power of the World Cup is just how much things can change over exactly one cycle. Four years ago nobody had ever heard of Christian Pulisic (RIP, temporarily). Four years ago, Neymar had just finished his first season with Barcelona; now there are rumors he could move to Real Madrid, and oh yeah, he currently plays for Paris Saint-Germain. Four years ago, superstars Mohamed Salah and Romelu Lukaku still technically belonged to Chelsea. Four years ago, the best players in the world were Lionel Messi and Cristiano Ronaldo. OK, fine. So not everything changes, but over the last four years, much of the soccer world has. Here’s what you need to know.

The Major Absences

As you are no doubt aware, the United States somehow managed to go on a miserable qualifying run in CONCACAF, capping it off with a loss to Trinidad and Tobago to lose their ticket to Russia. The USMNT is not alone among suprise failures, however. Italy isn’t at this World Cup, nor are the Netherlands, Chile, or Ghana.

Naturally, the USMNT’s loud failure has set off months of recriminations. It effectively cost Sunil Gulati, the president of U.S. Soccer, his job and led to plenty of hope for change, along with a fascinating political campaign that ultimately led to the election of ... Gulati’s no. 2, Carlos Cordeiro. Meanwhile, the USMNT is still without a head coach. There has been endless gnashing of teeth and rending of garments over pay-to-play academies and the lack of an open league system with promotion and relegation. All of which is entirely justified.

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And yet! The degree to which the United States isn’t alone also suggests that maybe, sometimes, these things happen. If Tim Howard had been a little less washed, or manager Bruce Arena had been a little less rigid, the U.S. would have been going to the World Cup despite the admittedly very real problems behind the scenes. Missing the World Cup is an extremely imperfect indicator for problems with a national team. The reasons can be very minor: The main culprit in Italy’s failure was manager Gian Piero Ventura refusing to play Napoli stars Lorenzo Insigne and Jorginho. Or they can be somewhat serious: The Netherlands had an alarming lack of new tactical ideas and a rapidly declining talent level. Or they can be near fatal: Ghana no longer even has a football association.

This is all symptomatic of what is both great and entirely unfair about the World Cup. It’s THE THING THAT MATTERS. International soccer is entirely built around qualifying for and winning major tournaments, but taking a snapshot once every four years is bound to exaggerate things in one direction or another. Four years ago, the Netherlands came in third place, and this year they weren’t even close to qualifying for the tournament, and in between they also failed to qualify for Euro 2016. However, the story is what happened around the events: Aging stars Arjen Robben and Robin van Persie, managed by an aging-but-accomplished Louis van Gaal, led one last-gasp run in 2014 that put a Band-Aid on a bigger problem.

It’s disappointing for the U.S. to miss this tournament. But the length of Tim Howard’s fingertips are not what determines whether a soccer nation’s national program is a success or a failure. The U.S. will probably be fine but flawed going forward, just like they’ve been for 20 years, and just like almost everybody else.

Back Three, Back Four, Who Even Knows?

For years, one of the truisms of soccer tactics was that there was a bright line between playing three center backs and a couple of wingbacks or two center backs between two fullbacks. Over the last four years that distinction has begun to fade away, and there are a handful of trends that led up to this current moment.

First, after years of asking fullbacks to patrol an entire sideline by themselves, managers started to realize that demanding one man both play as a winger in attack and not leave space behind himself defensively was impossible for all but a tiny group of people, most of whom played for Brazil. That was maybe not a huge problem during the days when one fullback would be tasked with being aggressive and the other would be conservative. However, as teams increasingly started playing with inverted wingers (right-footed left wingers and vice versa), they began to depend on fullbacks on both sides to add width. However, that made it increasingly easy for teams to simply counterattack directly into the space they’d vacated.

The solution was to have fullbacks do more work contributing as midfielders in possession of the ball, rather than pushing up the wings. Pep Guardiola aggressively played this way with Philipp Lahm at Bayern Munich, as well as his young understudy-turned-replacement Joshua Kimmich, who will feature for Germany this summer. Guardiola also currently starts England international Fabian Delph at left back at Manchester City. Many fullbacks will now step up the field and inside to do more of the creative work. This keeps them in more conservative positions in case the team loses the ball, and it allows the other attackers freedom to in turn do more dangerous work upfield. Which brings us to the line-blurring part of the story: What exactly is the difference between a fullback who steps in-field and contributes to possession, and a third center back who does the same? The answer: not a whole lot.

There was a time when lineups that played one aggressive winger-type fullback and one conservative defensive-type fullback were called a back four. Now that same arrangement of personnel—two center backs, one defender who likes to play as a winger, and one conservative fullback—is being called a back three, with the conservative fullback classified as a third center back. This has implications for the attacking setup since the conservative fullback/center-back player will have a wingback on his side of the field as well. But often times that wingback will just play as a full-on winger. In that case, the two wingbacks will themselves be unbalanced—and barely even wingbacks to begin with. One will be a fullback in disguise, and the other a winger. Is your brain hurting yet?

Kyle Walker, who mostly played as a right back for Manchester City, is going to be one of three center backs for England, and yet it makes total sense! England will be playing a 3-5-2 system, and Walker will be one of the three. But, as manager Gareth Southgate has pointed out in the past, he’s mostly taking up the same positions for club and country despite the different descriptions.

The shift in roles, and the shift in how we describe them, is a useful reminder that lineups are really only rough approximations of what’s happening on the field. The way they’re described tells you how commentators interpret the roles on the field, but now those roles are murkier than ever.

The Era of the Hybrid Forward Has Arrived

There was a time when playing a hybrid forward—part goal-scoring striker and part creative winger—was the provenance of only the very elite. Back when Cristiano Ronaldo transferred from Manchester United to Real Madrid in 2009, he was a one-of-a-kind monster who could both rinse you with stepovers before putting a cross into the box or get on the end of a cross from somebody else.

As Ronaldo has aged, he’s dropped the winger part of his game, and turned into a pure striker, but a generation of talent coming up behind him is now committed to doing both.

If you’re joining our soccer program late, you should really get caught up on Egypt and Liverpool’s Mo Salah. And if you don’t have time, just check this out. (Sorry for the music; that’s the price we pay for free YouTube highlights.)

Playing a hybrid right-winger role, Salah led the Premier League in goals with 32, and was second in expected goals (the goals Salah would be expected to score based on the historical conversion rate of the shots he took) with just over 25. He combined that with 10 assists, tied for fifth in the league (and tied for first among non–Manchester City players). Salah’s xGChain—that is, his total contribution to all of his team’s expected goals—of 35.30 led the Premier League. He plays for Egypt, so he’s probably looking at four games max in the World Cup, but he’s on the very short list of players who have arguably been as good as Messi or Ronaldo, even if it was for only one season.

Salah isn’t alone in his on-field complexity, either. This entire tournament is full of attacking wingers. Brazil’s major improvement has come because they’ve finally complemented their hybrid winger, Neymar, with a legitimate goal-getter in Gabriel Jesus. France’s young star Kylian Mbappé was a pure striker until a mega move to PSG saw him shunted out to a hybrid role. Opposite him, Antoine Griezmann is a star striker for Atlético Madrid, in part because he’s comfortable playing the role of winger when his team is out of possession. England have a pure striker in Harry Kane, but playing behind, beside, and generally all around him is Raheem Sterling, a hybrid attacker of the highest order. Further down the competitive ladder there are players like South Korea’s star, Tottenham Hotspur attacker Son Heung-min, who will play as a forward, and others like the trio of Eredivisie stars, Hirving Lozano of Mexico, Hakim Ziyech of Morocco, and Alireza Jahanbakhsh of Iran, who will all play as part of an attacking band behind a striker. Each of these players is comfortable attacking the box with the ball at his feet or taking on defenders and unsettling a defense in order to create a scoring opportunity either for himself or a teammate.

One of the major benefits of the hybrid forward (as opposed to a traditional striker) shouldering the scoring role for an underdog is that it’s simply much harder to prevent them from getting the ball. A pure goal-scoring forward, like Poland’s Robert Lewandowski, can be taken out of the game by a great defense. After all, you can’t score if you don’t touch the ball. Hybrid wingers are simply more involved in the buildup of attacks and sustained possession. They’ll come deep to get it if necessary and pull defenses wide to create space for other players (even if, on some of the lesser teams, those players will chronically let them down). Hybrid forwards used to be a luxury item, now a whole host of underdogs and favorites use them as foundational pieces.

The xG Revolution

Analytics in soccer has come a long way over the past four years. When the last men’s World Cup rolled around, expected goals was a bright, shiny new toy. Now it’s on BBC’s Match of the Day. All of a sudden it was possible not only to measure the number of shots a team takes, but to measure how good those shots were and then use that information predictively. From there, plenty more has happened.

First, those basic xG models have gotten better. Innovation and iteration have led to models that do more clever things with the data available. The maiden xG models typically only considered location on the field, phase of play, and maybe whether or not the shot was a header, but now they’re incorporating things like speed of play to better determine whether a defense is set. A more nuanced understanding of how incisive passes or timely dribbles might unsettle a defense means that xG models have continued to improve at the margins.

Second, the data itself is improving. Even as people get more clever with using it, there’s only so much that can be done with data that only tracks on-ball action. As one of the godfathers of modern soccer, Johan Cruyff, famously said, the average player has the ball for only three minutes each game, and so there’s so much more that happens across the full 90 minutes than just what happens to the guy with the ball. StrataBet has been calculating the number of players between a shot and the goal. And StatsBomb (where, full disclosure, I am the site’s managing editor) tracks the location of defenses and goalkeepers whenever a shot is taken, as well as when defenders pressure the ball. There is an effort underway to collect more complete data for analysts to work with.

Third, the concept of expected goals has been extended across the field. One of the metric’s biggest weaknesses is that it is built on measuring the value of shots, so players who don’t take a lot of shots naturally don’t get measured. That’s not a big deal on a team level—a team’s goal is to score more than they concede—but on a player-evaluation level, the metric was more limited when it came to describing midfielders and defenders. But now we have tools like xGChain and xGBuildup. The idea is simple: Take expected goals and distribute the credit backward to everybody who participated in the buildup to the shot. If a player is played in behind the defense for a one-on-one with the keeper, then the player taking the high-value shot (maybe as high as 0.6 or 0.7) gets credit for being there, the player playing the pass that set him free gets credit for the potential assist, and everybody within the chain of passes that got the ball to that point gets some small slice of the action, potentially going as far back as the goalkeeper who could have started the move from a goal kick. This gives credit to players who are consistently involved in creating high-quality chances for their teams, even if those chances are taken two or three passes down the line from when they had the ball. xGChain gives credit to everyone, including the shot-taker, while xGBuildup tracks, as the name implies, only the players involved in buildup play.

In this World Cup, Spain and Germany in particular are focused on drawn-out buildup play. Both squads are chock full of midfielders who want to keep the ball and pass the ball and keep and pass and keep and pass. Spain will likely cram five central midfielders onto the field at once. Barcelona’s defensive midfield-quarterback Sergio Busquets will look to control the field with club teammate Andrés Iniesta and former club teammate (and current Bayern Munich star) Thiago in front of him. David Silva and Isco, who are both mostly central attacking midfielders who excel at possession and creating chances, will patrol the wings even though they’re not your prototypical dribble-heavy wide players.

One potential problem that xGBuildup reveals is that of all those players, the legendary Andrés Iniesta had the weakest xGBuildup at only 0.52 per 90 minutes. He’s a living legend, but at 34 years old, it’s possible Spain would do better to start either a less accomplished player like Real Madrid winger Marco Asensio or a slightly more robust all-around midfielder like Atlético Madrid’s Koke as the fourth-best passing midfielder.

Like Spain, Germany has become obsessed with possession soccer. They have stocked the team with passing midfielder after passing midfielder to the point where they left Manchester City star winger Leroy Sané, who had 10 goals and 15 assists this past season, off the squad. They’ll also likely cram at least three pass-heavy midfielders into the team at once with Ilkay Gundogan, Toni Kroos, Mesut Ozil, Julian Brandt, and Julian Draxler all vying for minutes. With so many passers on the field at once, it’s nice to have a metric that can start to give them credit for the skills they are bringing to the table.

Instant Replay Is Not Your Friend

If you’re tired of feeling like a novice when it comes to occasional forays into soccer fandom, then there’s some good news. American soccer fans are way more experienced at hating instant replay than their European counterparts. Four years ago, goal-line technology made its debut at the World Cup without a hitch. This tournament’s step into the 21st century is the Video Assistant Referee.

Replay is a relatively new development in the soccer world. Only in the past calendar year have some leagues begun tentatively using it to review a limited set of decisions—specifically all goals, possible penalties, red cards, and instances of mistaken identity. The standard to overturn a call is the same as it is in American sports: It has to be clear or the decision on the field stands.

The problem with VAR is that the vast majority of refereeing decisions in soccer, even major ones, are judgment calls. Goal-line technology worked so well because the idea of whether or not a ball totally crossed the line doesn’t leave much wiggle room. Whether or not a player’s arm is in an unnatural position when the ball hits it in the penalty box, though, is endlessly arguable, and that’s why for time immemorial the referee has had to shrug and do his best to make a decisive call with minimal information. But having more information doesn’t really help.

American sports fans have, of course, been down this road before. Everybody knew what a catch was until the NFL started trying to regulate physics. The act of sliding into second base in baseball changed completely (and not for the better) once instant replay started letting umpires call players out if they came off the bag for a split second while a tag was applied. Using replay has all sorts of unintended consequences, and that’s just in sports where there is a demonstrably correct call the vast majority of the time. Soccer’s biggest refereeing decisions almost all exist within the gray area of judgment.

So, over the next month when arrogant soccer fans are looking down on your unsophisticated American ways and your rudimentary understanding of the finer points of the game, now you shall have your revenge. When the game inevitably slows down for a review and soccer fans begin to grapple with just how futile instant replay can be, you can just chuckle and sigh. They may have the experience with soccer, but American sports fans have all the instant replay ennui in the world.