They locked horns on numerous occasions while in charge of Spain's biggest two clubs, with both enjoying success.
However, it is the triumphs of two other managers that have resulted in them being involved in Friday's European Super Cup in Prague. Guardiola has inherited a Bayern Munich side that won the Champions League as part of a treble under Jupp Heynckes, while Mourinho has replaced interim boss Rafael Benitez at Europa League winners Chelsea.
Both Guardiola and Mourinho are unbeaten in competitive contests so far in their new roles, although their sides did only pick out draws last time out against Freiburg and Manchester United respectively.
German champions Bayern could be without vice-captain Bastian Schweinsteiger against the Blues after the midfielder picked up an ankle complaint against Frieburg.
Meanwhile, having started the game against Man United without a recognised centre-forward, Mourinho is believed to be considering using Fernando Torres from the outset.
Possible starting lineups
Bayern: Neuer; Alaba, Dante, Van Buyten, Lahm; Kroos, Schweinsteiger; Robben, Gotze, Ribery; Mandzukic
Chelsea: lineup Cech; Ivanovic, Terry, Cahill, Cole; Lampard, Ramires; Hazard, Oscar, Mata; Torres
Sports Mole says: 3-1