Pep Guardiola has challenged sextuple winners Bayern Munich to take on his old Barcelona side that achieved the same feat in 2009.
Barcelona are the only other side to have won all six trophies available to them in a year. With Guardiola guiding the Catalans, Lionel Messi scored an extra-time winner against Estudiantes in the Club World Cup final in December 2009 to complete the set.
Watch: Guardiola led Bayern to the 2015/16 Bundesliga title
"Big congratulations to all [the] Bayern family for this incredible success," the current Manchester City boss said in a message released by the German champions. "We are so proud - I am so proud. A big congratulations for everyone and especially Hansi, the players, and the backroom staff for this amazing thing.
"But I would like to say to Hansi that you are the second team to win the six titles in a row. Before it was another team - it was Barcelona. So maybe I can call Messi and company, and we can play for the seventh title. So tell me when and where, and we will be there!"
Guardiola had a twinkle in his eye when he suggested the battle of two record-breaking outfits, and Bayern's 2021 team facing his Barcelona side of 2009 would be quite the encounter.
After seeing off all comers in the Bundesliga, DFB Cup, UEFA Champions League, DFL Supercup, UEFA Super Cup and now the Club World Cup, Bayern would certainly be confident. All the more so with Manuel Neuer, Alphonso Davies, Joshua Kimmich, Kingsley Coman, Thomas Müller, and Robert Lewandowski in their line-up.
Barcelona would also fancy their chances if they were able to roll back the years, though, with the likes of Messi, Dani Alves, Carles Puyol, Xavi, Andres Iniesta, Thierry Henry, and Zlatan Ibrahimovic to call on.
Guardiola, of course, would have the advantage of knowing Bayern inside out. The Spaniard was in charge of the Bavarians from 2013-2016, winning three Bundesliga titles, two DFB Cups, the 2013 UEFA Super Cup and the 2013 Club World Cup.