In a season that sees Lionel Messi mounting a brutal challenge to seal his fifth Ballon d'Or, it tells you a lot that Ivan Rakitic is already firm competition to his teammate for Barça's player of the year award.

That Barca are in contention to win a second treble in three years owes a lot to the Croatia midfielder, who has proved not only his stamina but his intelligence, leadership, and constant hunger for success this season. It's his best since signing for Barcelona in 2014. But that all of this is true is remarkable given that what Rakitic is actually doing would have been prohibited under Johan Cruyff, Pep Guardiola, Tito Vilanova -- not too long ago, it would have been booed out of the stadium by Barça purist fans, too.

For the longest time, certainly since Frank Rijkaard took over in 2003, the vastly pre-dominant Barça formation has been 4-3-3. Because we live in an age of analysis, of breaking football down into component parts rather than the old way of enjoying the whole while letting strategy wash over us all, the nuances of 4-3-3 have been endlessly put under the microscope.

What is abundantly clear is that it feels and looks like a buccaneer, flamboyant and attacking protocol, but it's also a taxing, technically demanding and ultra-athletic formation.

When Xavi, Sergio Busquets and Andres Iniesta were in their absolute prime, it was regarded as "sinful" to crowd the midfield with more players when two wide men could be added to the central striker up front instead, in order to press, add width and drag opposition defences wide so that space opened up around the last third of the pitch. Then, in the era of the "Tridente" (Messi, Luis Suarez, Neymar) up front, it was obligatory that Barcelona played with just three (rather than four) starters in midfield regardless of how that formation shifted its shape during the ebb and flow of a match. It demanded that the position Busquets occupied was even more fundamental to the intelligence of the entire team's performance.

Here in Spain, they call the central midfielder the "pivote," which is in effect a term stolen from basketball's "pivot." In England, they persist in calling that player a "holding" midfielder. It tells you something. Something negative. For those who apply that term, it's about holding back the opposition, augmenting the barrier in front of the centre-backs: a player who can suffocate, tackle, block. A terrier.

For the majority of Spanish teams, the "pivote" is about so much more than that: brains, positioning, restarting the play, choosing brilliant forward passing options, regulating the tempo of both defensive and offensive play, alternating the "line" that a team holds and often moving into the space where an old fashioned No. 10 would have played if the opposition is ultra defensive.

It's the position Galileo would have played had he been a footballer.

Rakitic has emerged as the natural heir to Barcelona's most important midfield role. Miquel Llop/NurPhoto via Getty Images

All of which explains why Busquets has become justifiably regarded as one of the great modern footballers. He's a post-war great worthy of comparison with Franz Beckenbauer, Lothar Matthaus, Matthias Sammer, Roy Keane, Patrick Vieira. Greats like them.

In his time, Busquets' performances have meant that his club could shed: Edmilson, Rafa Marquez, Seydou Keita, Thiago, Yaya Toure, Cesc Fabregas and Alex Song. Mr. "Bring It On" Busquets. Try as they might Barça haven't, until now, found someone who can mimic his vast array of talents.

Then Ernesto Valverde did two things. Firstly he ripped up the template. The Basque coach decided something: "Why must it be the case that Barça always play 4-3-3 if the personnel in the squad dictate otherwise?"

He knew that Iniesta, aged 33, couldn't be racing up and down the pitch as in times of old. He knew that Busquets -- about whom 38-year-old Xavi recently joked "I'm still quicker than him!" -- wasn't a guy who could be dragged about the pitch if possession was lost. Busquets' ideal is about controlling space, controlling possession, dominating the playing arena and not being buffeted about by a game.

So Valverde installed the idea that there would be two "pivotes" in almost all of Barça's formations this season, and four men in midfield. What was literally a "dirty" phrase in the past around the Camp Nou was now reality.

Even in the 2010 World Cup, when Spain won and the Xavi-Busquets-Iniesta partnership was at its absolute peak, there was a hell of a fuss about "doble-pivote." Vicente Del Bosque wanted organisational security so he paired Xabi Alonso with Busquets. The Barca trio were convinced that Busquets was sufficient on his own while the hawkish Spanish media rounded on Busquets after the opening group game defeat, to Switzerland, stating that a "doble-pivote" was "negative" and that Alonso could do the job on his own.

"Doble pivote" remains an emotive phrase in Spain, but partnering Rakitic and Busquets at the heart of a four-man Barça midfield has been an outrageous success. Not only because they are 38 games unbeaten in La Liga, preparing for their fifth straight Copa final and have one foot in the Champions League semifinal. Rather because when Busquets is rested, injured or suspended, Rakitic the apprentice has proven able to then take on the job, on his own, to an outrageous degree.

It's almost unfair on other clubs that Barca has not only Busquets, but also the closest thing to a "Busi" facsimile you'll find anywhere in Europe. Multiple times this season, Rakitic has bossed a game -- positionally, with his interceptions, with his passes, with the sense of order and tempo he gives matches -- from central midfield. Turning 30 and running more than any other Blaugrana player in European competition this season hasn't stretched him.

Busquets and Rakitic form the essential midfield double-pivot that was once anathema at Barcelona. David S. Bustamante/Soccrates/Getty Images

Playing more minutes in La Liga by Game 30 this season compared to the entire league last season, more Champions League minutes than in 2016-17, travelling back 5000 miles with jet lag from having played in Dallas during the international break to then play dominantly against Sevilla, Roma and Leganes. All of this has been meat and drink to him.

Rakitic has had iconic moments, too. Think of him racing away from Luka Modric in the December Clasico in a run that opened up Barcelona's 1-0 lead in what would be a 3-0 win. He's the blond-haired lad you see nicking the ball all the time, like 207 times in 30 Liga matches (50 in the Champions League), for example. His passing is exemplary: he's currently one short of 2000 accurate passes thus far in la Liga (630 in Champions League). Against Betis in La Liga, he also broke the deadlock with the counter-attack goal to remind us of how he used to play: box-to-box. There was another left-footed finish past Gianluigi Buffon to get Barça's season kick-started in a 3-0 win.

The fact that Rakitic is in this form, right now, is apt. Tuesday night means a return to face the guy who didn't so much "discover" him as unleash him. Monchi, Roma's brilliant director of football, was the guy who tracked Rakitic for months and months before taking him from Schalke to Sevilla. There, Rakitic found trophies, found fame, found a wife and found a platform to greatness... at the Camp Nou.

Recently Monchi admitted: "I've always said that my best-ever signing was Dani Alves. Now I'd have to put Ivan [Rakitic] up there at that level and if there were one player I could take from Barca right now, beyond Messi, it'd be Rakitic."

Wise words from a wise man but they'll fall on deaf ears, I suspect. Rakitic, the former architecture student, has found a home at the Camp Nou and he's the foundation of the empire they're currently trying to build.