No qualities define Vicente del Bosque's Spain better than team harmony, continuity and trust. From top to bottom, from manager to players to support staff, there's a rarely celebrated but obvious bond that underpins the success of this La Roja era.
As World Cup and European Championship crowns have been captured, it's been elementary to highlight the unparalleled talent that resides within the Spanish dressing room, the once-in-a-generation players such as Xavi, Iker Casillas and Andres Iniesta, a fabled Barcelona core that has made everything tick, all steered by the most decorated manager in the game.
But it's the cohesion of it all that is too easily overlooked, a selflessness and unity that has made it all possible.
In that sense, Diego Costa is Spain's outlier.
He's the piece that has the potential to give Del Bosque's men a whole new dynamic. But he's not a natural fit. His disposition doesn't align with the character of his national team.
"One of the fundamental issues is the good relationship that exists within the group," Del Bosque told World Soccer's Jamie Rainbow in 2012. "I have been fortunate to have a good group made up of nice people. It is important to reinforce the relations that exists between the players—that was a key part of our success in recent years."
When Costa cut a dejected figure heading to the bench after just nine minutes in the UEFA Champions League final in Lisbon, it felt like a critical moment for Spain as much as it did for Atletico Madrid.
The striker had taken a high-stakes gamble on his fitness at the expense of his team, attempting to defy science by returning from a Grade 1 hamstring tear in the space of seven days.
It proved costly. Real Madrid ran all over a Rojiblancos side that had nothing left to give in the dying stages of a historic European final.
Are we to believe that Costa felt he was fully fit? Surely he and Diego Simeone discussed the situation and prognosis? The gamble must have been a joint decision, mustn't it?
That's all speculation, but what Costa's early exit showed us wasn't just that science is nigh-on impossible to defy.
No, more tellingly, the 25-year-old's wild punt in the dark was an indication that Costa's mentality is in the Simeone mould rather than the Del Bosque one—it's all high-octane stuff, guided by raw emotion, passion and unrelenting energy.
Simeone and Costa would have known the risks heading into that final, but they allowed their clarity to be muddied by the heat of the moment. Basically, emotion took over.
That's not Del Bosque. That's not Spain. The world champions play the odds, trust the system, stay composed and are prepared to live with the results that process brings.
So now, how far does Spain's trust and team harmony extend in relation to Costa? In his battle to regain both fitness and form for the impending World Cup, does he possess the judgement to make the right call for his team, regardless of what that means for his own personal achievements?
He might. I hope he does.
But we don't know.
And based on recent evidence, neither does Del Bosque, which is why Costa is a headache for the Spaniards and their manager.
Yet, it gets more complicated. In fact, the Costa headache is perhaps more of a conundrum. He is, after all, a gun striker, representing a possible antidote to Spain's documented lack of firepower. As mighty as they are, Del Bosque's team craves a potent finisher, the sort that would elevate La Roja to unprecedented levels.
If it worked, can you imagine it—the brilliance of Xavi, Iniesta and Co. linking up with a truly prolific striker ready to pounce with precision on the plethora of chances created for him?
The manager will want to deploy him. Based on his squad, he actually needs to.
Of Spain's alternatives, the most in-form goal-scorer that was available to Del Bosque—Fernando Llorente—didn't make the final 23-man squad. Neither did Alvaro Negredo, who, despite a poor run of form since January, could have given the Spaniards a different look.
Of those who were handed a ticket to Brazil, Fernando Torres and David Villa scored one league goal between them in 20 combined games from early March onwards. Cesc Fabregas, who regularly plays as Del Bosque's false nine, hasn't scored since the beginning of February (both stats via WhoScored.com).
It all gets back to that continuity and team harmony. Torres and Villa have been selected because Del Bosque trusts their ability to be cohesive with the rest of the squad both on and off the field.
Costa, however, is the man that could be the difference. Yet, it's all ifs and buts for the Atletico Madrid star. The potential, if it worked—"it," in this case, meaning a seamless transition for Costa into the Spanish team—is scary.
But untried and untested is not how Del Bosque likes them. You only need to look at his final squad to know that.
Del Bosque may harbour other concerns for Costa, too. Will he thrive in the team's Barcelona-esque style despite starring in a counterattack-based system in Madrid? Can his feisty nature on the pitch blend with the cool personas of those around him? Among La Roja's players, perhaps only Sergio Ramos competes with a similar rawness and unrestrained fire.
Those issues, however, are minor ones. More pertinent to the manager will be the instability and volatility set to surround Costa this summer.
At the top of Chelsea's priorities is signing the prolific forward before he flies to Rio de Janeiro, according to The Telegraph's Matt Law. While the reported big-money move represents due recognition for the 25-year-old's achievements, it must be remembered how challenging a move to England may be for Costa.
After learning his trade on the streets of Brazil, the forward has only ever played professionally in an Iberian environment. An impending and drastic change of culture, language and surroundings doesn't exactly provide Costa with a sense of stability and continuity in this pivotal summer.
Uncertainties exist everywhere, but guarantees are few and far between.
Then there's the public-enemy status he'll hold during this World Cup in Brazil—the country of his birth that he snubbed in favour of Spain. Dealing with that peripheral turbulence will require clarity in the mind, as well as extreme levels of tolerance and patience.
Does he have that? Even just a little bit?
The headache. The conundrum. Whatever you want to call it, it's there.
Costa could blow apart the whole tournament for Spain and propel La Roja to a romp to the title, adding bite to the most fluid machine in world football.
But the possibility is there for it all to go the other way, too.
It's all an unknown.
Just the way Del Bosque doesn't like it.