Whether they are fine-tuning title-winning teams or completely revamping underachieving squads, the coaching staff and recruitment strategists at Europe's elite clubs will all head off on their summer holidays with one common quandary in mind: just how is anyone supposed to beat Barcelona?
Any club with ambitions of winning next season's Champions League knows they will likely have to wrench the trophy from the Catalans' grasp in order to do so, but serious setbacks for Pep Guardiola's side have become as rare as a misplaced Xavi pass.
In fact, since Guardiola succeeded Frank Rijkaard in June 2008, Barcelona have been beaten just three times in encounters they absolutely could not afford to lose: by Sevilla, in the 2009-10 Copa del Rey last 16; by Internazionale, in last season's Champions League semi-finals; and by Real Madrid, in the final of this season's Copa del Rey. There have been other defeats, but those three teams are the only ones to have overcome Barca in competitions they were desperate to win.
It can be little coincidence that two of those sides - Inter and Real - were coached by José Mourinho. One of the game's foremost tactical thinkers, Mourinho realises that playing Barca at their own game is tantamount to suicide. Accordingly, with a 3-1 lead to protect from the first leg in the 2009-10 Champions League semi-final, he instructed his Inter team to sit deep, concede possession and form a tight defensive block on the edge of the penalty area. By defending with astonishing discipline and positional awareness, they produced one of the great reactive performances in modern football history.
This season's Copa del Rey final told a similar story, with Barca beaten by a Real side in which Pepe was deployed in midfield to create as much congestion in the middle of the pitch as possible. The team that came closest to beating Barca in 2008-09, meanwhile, was another Mourinho project: Chelsea, who rattled Guardiola's men with a muscular, committed showing in their Champions League semi-final and would have progressed to the final had it not been for a jaw-dropping injury-time equaliser by Andres Iniésta in the second leg.
Mourinho realises, as few other managers have, that beating Barcelona requires a team to abandon its own playing principles and focus almost exclusively on knocking the opposition out of their stride. Manchester United failed to do so in Saturday's Champions League final - Sir Alex Ferguson claimed that making special arrangements for players such as Lionel Messi was "alien" to the club's principles - and paid exactly the same price as they had in Rome two years earlier.
Part of Barca's majesty is the inevitability of their successes. Their artistry with the ball and breathless endeavour without it mean they are guaranteed to dominate possession in every match they play, meaning they create more chances and concede fewer sights on goal to their opponents than almost any team in history. Furthermore, their team is the product of a playing philosophy over 20 years in the making, ever since Johan Cruyff returned to Camp Nou in 1988 and made the 'Dutch way' the focus of his vision for the club's future.
For a coach like Mourinho, who prides himself on requiring just two seasons to transform the fortunes of a club, an adversary like Barcelona with such a deeply ingrained playing style represents the very antithesis to his methods. The Portuguese, however, is sufficiently canny - and respectful - to realise that Barca's current playing formula demands tactical subordination from any team who dreams of beating them. Ferguson and the continent's other top coaches will need to catch on quickly, because the only current threat to the dominance of Guardiola's side is time itself.