Real Madrid superstar Cristiano Ronaldo has suggested his boss, Jose Mourinho, is the world's best coach, even ahead of the likes of Sir Alex Ferguson and Roberto Mancini - so, who is the current best manager in the world?
The question is riddled with problems. How do you define the best coach? Most titles, most influential philosophy, most tactically astute, most domestic leagues, most Champions Leagues, perhaps even the most attacking.
Ultimately, it's likely to be a combination. Sir Alex Ferguson may claim the most titles, but that doesn't necessarily mean he's the best manager in the world right now.
He could have already reached his peak in his managerial career, there may be better, younger coaches more deserving of the mantle at this exact moment in time.
And that's the key point - this exact moment in time. To be considered the world's best you must have demonstrated your worth in the near past.
So Arsene Wenger's unique achievements with Arsenal in the late 90s and early 2000s no longer hold much weight.
He very reasonably could have been the world's best in 2004 - after his side went unbeaten for an entire season - but after seven years without trophy his claim is weak.
So who's is strong? Well, top of the pile must be Pep Guardiola. It's a curious phenomenon that dictates a person out of action seems to become more valuable - Jack Wilshere for Arsenal and England a recent example.
And Guardiola's stock has never been higher - even though his final season at Barcelona ended in failure - in the sense they didn't win either league or cup despite possessing the best team.
In four years at the Nou Camp, Pep won three La Ligas, two Copa Del Reys, two Champions Leagues, and two Club World Cups. In total, including a few minor pieces of silverware, Guardiola took home 14 trophies in four seasons. Every year he was named La Liga Coach of the Year.
In Lionel Messi's own words, Guardiola "is the best coach in the world and wherever he now chooses to go he will be a success, I have no doubt about that."
An endorsement from a three-time Ballon d'Or winner is influential, as much as the clamour now for his signature is flattering. No other manager has had such success in recent history. But who else deserves to be considered?
Head of the queue is Jose Mourinho - the man who pipped Guardiola to the La Liga title last year. According to Cristiano Ronaldo, he's the best coach in the world, and according to the stats, the Portugal international's got a point.
Two Champions League titles with two different clubs, domestic league titles in four different countries, and bettering Guardiola and the mighty Barcelona machine in La Liga.
The Special One has established himself as the premier coach in every country he's managed in - and he's managed in the three biggest, England, Spain and Italy.
He gets the best players to play for him, the likes of Frank Lampard, Didier Drogba and John Terry at Chelsea, Diego Milito, Wesley Sneijder and Lucio at Inter Milan, and Cristiano Ronaldo, Sergio Ramos and Iker Casillas at Real Madrid.
He promises to return to England after he's finished at Real Madrid, but in truth, he has the pick of every club in the world - just like Guardiola. Because it's not just his record that speaks volumes, it's his character, his cult of personality that attracts the best players and moulds them into coherent, title-winning teams.
Sir Alex Ferguson has done this to a similar extent at one team, building in cycles, but Mourinho has successfully exported the trick to every side he's managed.
In England the candidates are few and far between. The Chelsea hot-seat has proven too fierce for even skilled tacticians like Carlo Ancelotti, while Arsene Wenger has struggled wilfully to keep pace with the big-spending top teams.
Of course, there's Sir Alex Ferguson. The Manchester United manager bestrides the Premier League like a colossus. His record across the last 25 years is without parallel, and for that reason he deserves a place at the top table - perhaps even at its head.
These three managers are the game's best, but each for different reasons.
Guardiola for intense, unprecedented success at one club in a concentrated period of time. Mourinho for sustained success across many clubs in many countries - displaying an adaptability few else exhibit.
And Ferguson for longevity, for his success at one of the world's biggest clubs, and his capacity to rebuild, rejuvenate and reinvigorate when others would walk away.
How about some other contenders? The likes of Jurgen Klopp at Borussia Dortmund - back-to-back Bundesliga champions and flying top of a Champions League group including Real Madrid and Manchester City.
Or perhaps Mauro Biesla at Athletic Bilbao, if not for his success, then at least in recognition of his commitment to exciting, vibrant attacking football.
Fabio Capello has the pedigree, but no longer the stage, to cement his place as one of the best manager's in the world, and his legacy, in England at least, is unfairly tainted by his spell in charge of the national team.
Carlo Ancelotti is another with a hugely impressive track record, and, whisper this quiety around Stamford Bridge, Rafael Benitez actually has a pretty impressive CV. Two Champions League finals with Liverpool and a couple of La Ligas with Valencia.
So do you agree with Ronaldo, or perhaps you side with Messi? Or maybe Sir Alex Ferguson, or maybe even another? Who do you think is the best manager in the world at the moment? Leave your choice below...