There are many obligations incumbent on the president of Barcelona football club, encompassing success on the pitch, style of play, Catalan identity and staying ahead of one team in particular from Madrid, although in the modern era one requirement has stood out above all: keep Lionel Messi happy.
It is a simple duty to the greatest one-club footballer of this era or any other, an individual whose importance to Barcelona is on a level removed even from the other great one-club figures of recent history.
Steven Gerrard, Ryan Giggs, Paolo Maldini, Francesco Totti, Tony Hibbert - none of them have succeeded in the way Messi has at Barcelona.
The club were already 104 years old when he made his debut in 2003, an institution of great renown that could claim to have reinvented the game once. It only goes to demonstrate the scale of Messi's effect that he is the club's greatest-ever figure, when there is such competition in that regard.
Josep Maria Bartomeu, Barcelona president: you had one job. The Instagram excoriation on Tuesday by Messi of sporting director Eric Abidal, a former team-mate, was the boiling over of the long-running feud between Barcelona's board and its greatest player. A consequence of the management of Barcelona's finances, and an indicator that even the club who claim to be better than everyone else, owned by their fans, are capable of the kind of misjudgments even the most crass owners might make.
At 32, Messi is still a long way from being the old favourite granted a few minutes off the bench and eyeing a Major League Soccer sinecure. He won the Ballon d'Or in December, he has 19 goals in 24 games this season.
As to the bigger picture, he remains the club's marquee name, not even close to being usurped by a young pretender. He is the principal reason the global audiences subscribe and spend and click, an inscrutable little emperor whose retirement one day will be an occasion as solemn as a state funeral.
The relationship between Bartomeu and Messi has disintegrated over time, with occasional truces for picture opportunities intended to demonstrate solidarity. Meanwhile, Abidal was one of the few former players who could be persuaded to work with the board. His ham-fisted attempts to appoint Xavi as the successor to Ernesto Valverde over Christmas culminated in this week's interview in which he criticised the Barcelona players for undermining the former manager, chiefly by not working hard enough for him.
That was the trigger for Messi, who, among other things, called upon the club's hierarchy to "take ownership of the decisions they make", which begs the question how Abidal survives or, indeed, whether Bartomeu can stay in the post beyond this season.
He is due to step down in the summer of next year and endorse a continuity candidate in the subsequent presidential race. Whoever that is will have to defeat Joan Laporta, former incumbent and presumed favourite of Messi, as well as the new contender, Victor Font, who has the backing of Xavi.
What kind of Barcelona they will inherit is another matter. Bartomeu has presided over a spiralling wage bill that is budgeted to be €671 million across all sports for the current season. The signing of Antoine Griezmann from Atletico Madrid in the summer for his €120 million buy-out fee was only possible because the club borrowed against the value of the outstanding liabilities owed by their creditors. Messi, and the older guard in the squad, including Luis Suarez, were as open as they have ever been about a preference for re-signing Neymar.
The Valverde sacking, the first midseason dismissal of a Barcelona coach since Louis van Gaal in 2003, was a bloody affair, and its aftermath - Abidal's attempt to blame the players - could be the most damaging part yet.
On one side is Messi and, on the other, Bartomeu, scion of Catalan industrialists who manufacture boarding bridges for airports and ferry terminals. In September a Spanish YouTube personality claimed Bartomeu had reported him to the police for a tweet in which the Barcelona president was referred to as "Nobita", a Japanese animation character synonymous with failure. The case did not progress to criminal charges.
He presides over a club who had won the league in the past two seasons under Valverde but seemed to feel that something fundamental was lacking.
The fragility of the club's decision-making was epitomised by the way in which that unexpected defeat by Atletico in the meaningless Super Cup in Saudi Arabia progressed to Valverde's sacking and a full-blown crisis. Like Manchester United, they desperately needed a striker in the January window after injuries to Suarez and Ousmane Dembele, and it was then financial weakness was laid bare.
But the club have always had Messi to fall back on. While he has threatened to leave in the past, it has only ever been as part of the chess moves over his contract negotiations. Even this summer there is doubt as to whether his contract permits him to walk away from the club, or at least that he can sign for a rival in what is regarded as a competitive league - which would leave either MLS, or somewhere further afield.
The more likely outcome is that he will outlast Bartomeu, whose handling of the last few months has demonstrated once again who holds the power at the club. Yet the problems to which Messi has alluded go far beyond the sacking of Valverde or the failure to sign a striker.
For now, the little maestro still has it within his power to save the club, as he has done so many times in the past. The next president will be closer to the time when that option is no longer available. (© Daily Telegraph, London)