Football is, first and foremost, a team game. Teams win championships, trophies and leagues.
But as our collective vivacious appetite for individual awards—such as the Ballon d'Or, the Player of the Year and even Man of the Match—suggests, there's plenty of room to discuss the individual.
Here we identify each of Europe's top teams' "Jenga piece"—the one whom without, the team falls apart. It's less "best" player and more "vital" player, the key or irreplaceable cog that greases the entire team's wheels or justifies their style. In some cases, where it was a close call, we've listed an honourable mention.
Note: For a longer look at why these 10 teams in particular have been chosen, look here. They've been listed here in alphabetical order.
Barcelona: Lionel Messi
Barcelona without Lionel Messi is—fortunately for them—a reality we don't see too often.
Availability has always been a strength of his, starting 40 or more games every year for the past decade, so he is someone you can afford to build around.
But even demigods come down with the odd injury, and Messi has missed some time here and there. An example of that was the beginning of this season, when a three-game run without him saw Barca pick up just four points against Athletic Club Bilbao, Real Betis and Osasuna.
La Blaugrana have tried to diversify their attack so that they aren't quite so reliant on Messi, but it's tough for two reasons. First, because he's literally irreplaceable, the best player in the world, and second, because other top-class attackers have struggled to coexist in an environment where the plan is understandably simple: Give it to No. 10.
Bayern Munich: David Alaba
One of this season's most surprising (but incredibly effective) developments has been the remodelling of David Alaba. Once a left-back-cum-central-midfielder, he's now a commanding centre-back who leads the defensive line of what feels like the strongest team in the world.
Injuries and the rise of Alphonso Davies at left-back were key factors in the reshuffling of Bayern's defence, with Alaba asked to shift inside initially because there was no other choice. He won't be moving back any time soon, though; he's proved far too important in so many facets of the game to do so.
One of the benefits of the behind-closed-doors matches being played is you get to hear who the most vocal players are, and it feels like Alaba never, ever stops talking. Even alongside the uber-experienced Jerome Boateng, he's commanding the depth of the line and handing out instructions all the time.
His slickness on the ball is vital to Bayern's build-up play down the left, while his mobility means he can cover the large spaces Davies leaves when he speeds forward in attack. You'd think a player like that might be weak aerially, but Alaba was seen outmuscling and out-jumping Erling Haaland in Der Klassiker in May.
Bayern are a fierce attacking force, but that's courtesy of six or seven players who all chip in. They're a defensive wall thanks to Alaba, though, who performs arguably the most singularly important role in the team.
Honourable Mention: Thomas Muller
Borussia Dortmund: Mats Hummels
In signing Mats Hummels last summer, Dortmund acknowledged the need for a "veteran presence" in their defensive corps.
That phrase gets overused, with its meaning somewhat strained as a result, but in Dortmund's case, it was clear: A litany of defensive errors and implosions pretty much cost them the title in 2018-19, so adding a player of Hummels' ilk felt like a logical move.
It's proved so—even if Dortmund have once again placed second to Bayern—as this time they have been bested by what is essentially the best team in the world rather than their own mistakes.
They've looked far more composed in defence and have conceded fewer goals per league game—though they did have to change formation to hit form. Hummels has been at the centre of that new shape, too, marshalling and commanding with an assuredness no other can provide.
Juventus: Cristiano Ronaldo
Like with Messi and Barca, it's hard to escape the simple reality that Cristiano Ronaldo is Juventus' Jenga piece.
When a player is this good, they're naturally going to be the focal point for so much of the team's play, and what accentuates that fact in Ronaldo's case is that Juventus, even after almost a year with Maurizio Sarri at the helm, lack a discernible style of play and therefore rely on individuals to a greater degree.
The Portuguese began 2020 with a nine-game scoring streak, his goals making the difference in a series of games. On plenty of occasions in 2019-20, when The Old Lady has looked a touch discombobulated, Ronaldo has stepped forward to rescue the situation.
That is, has been and always will be what he does best.
Lazio: Francesco Acerbi
The goals flow freely up top for Lazio.
Their 60 Serie A strikes from 26 games is a record bettered only by Atalanta's tally (74), and they draw them from various sources: Capocannoniere-elect Ciro Immobile (27) has been monstrous, but Felipe Caicedo (eight), Joaquin Correa (seven), Sergej Milinkovic-Savic and Luis Alberto (both four) have all chipped in, too.
In contrast to that shared effort, there's one particular presence at the other end of the pitch that towers above everyone else: Francesco Acerbi, the man with the most heartwarming story in football but also one of the best centre-backs in the game.
Acerbi has recovered from cancer—twice—during his career, and that storyline understandably dominates his personal narrative. What can be forgotten or left aside, as a result, is what a fine player he is, and he's spent his entire tenure at Lazio reminding us weekly of that fact.
Lazio's goals are impressive, but perhaps even more so is their impeccable record at the back: They've conceded the fewest in Serie A—just 23 in 26 games—with Acerbi an almost ever-present rock at the back. His mix of ball-playing prowess and defensive acumen, plus his leadership skills, make him the most crucial cog.
Honourable Mention: Ciro Immobile
Liverpool: Virgil van Dijk
The Virgil van Dijk-Liverpool case is similar to the Alaba-Bayern case; with an embarrassment of riches up top, it's hard to pinpoint one single attacker, whereas further back, there is a man who has a significant influence in the structure, mentality and overall performance of the team.
Since the day the Dutchman walked through the doors at Anfield, things have been different. It's easy to forget, but before he arrived, the Reds were an incredibly leaky side, having to outscore opponents to win games.
He wasted no time changing that, posting 10 clean sheets in the first 22 matches he played for the Reds.
His ever-present nature means he's missed just three league matches since signing—he started all 38 games last season and is on 30/30 this term—so we can only compare the teams in pre- and with-Van Dijk forms
The former was exhilarating but error-prone and volatile in its form; the latter is a European champion and soon-to-be Premier League champion in an uncompromising sledgehammer of a side that has crushed opponents for 18 straight months.
Manchester City: Aymeric Laporte
The knee injury Aymeric Laporte suffered in September caused Manchester City all sorts of problems. The Frenchman missed the rest of the calendar year, and there were times when they looked lost (defensively) without him, with his absence compounding Vincent Kompany's departure in the summer.
In the grand scheme of things, they didn't drop too many points—just seven in the league—but the machine looked short of a few bolts in a few squeaky wins, and one loss came to Liverpool, who just relentlessly won games and soared clear at the top.
Laporte's injury pushed Fernandinho to centre-back and introduced Rodrigo to the rigours of the Premier League week in, week out—something he probably wasn't 100 per cent ready for at that stage. It wasn't just that one of the world's best defenders was missing; the chain reaction his injury caused (and some poor squad planning along the way) destroyed City's league campaign.
With Laporte back in the side, the machine looks slick and well-oiled. If they are wise, they will take precautions to ensure this doesn't happen again.
Paris Saint-Germain: Angel Di Maria
In 2020, Paris Saint-Germain have been able to do something that not even their own manager, Thomas Tuchel, thought possible: Find success using a 4-2-4 formation that utilises all four of their star attackers.
"For me, it's not balanced enough at this level. I think it's absolutely necessary for us to play with three midfielders. I really get the impression that everyone thinks it's normal to play with four forwards. I'm convinced that it's not possible," Tuchel told RMC Sport (h/t B/R's Tom Williams) in November when pressed to put Kylian Mbappe, Mauro Icardi, Neymar and Angel Di Maria in the same XI.
Sounds unequivocal, doesn't it?
Well, fast-forward a few months and PSG are indeed rolling out four star attackers at once and finding a balance Tuchel suggested was impossible. The key? Di Maria, whose versatility and pliability, plus his devilish work rate and team ethic, is the glue that holds it all together.
He has the finesse and quality to be considered one of their Fantastic Four but also the grit to work back against the ball and help what would be an exposed midfield. His playing personality seems to have rubbed off on others, too; Williams explained in January how Neymar was showing increased defensive consciousness.
RB Leipzig: Timo Werner
RB Leipzig boast great depth, great flexibility and versatility and seem to be able to point to several players for each role they require, except one: chief goalscorer.
It's hardly a bold statement, but no other forward in Die Roten Bullen's ranks can score at the rate Timo Werner can. Yussuf Poulsen and Patrik Schick are the hold-up guys; Christopher Nkunku and Dani Olmo are goalscorers but from deeper positions. And Jean-Kevin Augustin is out on loan, seemingly expended.
No one does what Werner does, not even close; he's on 32 goals for the campaign with one more game to go, while Schick is way back on 10.
What will worry RB Leipzig is that their key piece is soon to be gone. Chelsea have agreed to sign him, and the German will link up with the club in July, meaning Werner will miss their UEFA Champions League push in August. They're a distinctly lesser side without his threat, and with him probably goes their dark-horse shot at lifting the trophy.
Real Madrid: Karim Benzema
Karim Benzema is so entrenched in Madrid's attacking play that it's a wonder as to whether anyone else can succeed in the team until he's long gone.
For more than a decade, defenders and midfielders in white have looked for his clever runs, either splitting to the left or dropping deeper centrally, to build attacks. His football IQ is off the charts, while his movement and control in tight spaces are rivalled by few other No. 9s.
Back in the days of the BBC (Benzema, Bale, Cristiano) combo, his selfless movements were the key to creating countless chances for the wide men. His connection with Marcelo was telepathic too.
Post-Ronaldo, he's only grown in importance. Madrid are weaker in attack and are ushering through a new generation, making him the star of the line in a team that is more workmanlike and gritty than luxurious nowadays.
He's still at the heart of it all, ducking, weaving and creating, while his form in front of goal has reached new levels of brilliance.
Honourable Mention: Casemiro
All statistics via WhoScored.com.