The super club era, and the resulting repetition in the Champions League knockout stage, means it was inevitable that Bayern Munich coach Pep Guardiola would meet old club Barcelona at some point.
It's somewhat fitting that it comes in at the semifinal stage, because the 2013 semifinal between Bayern and Barca was effectively when Guardiola's reign at Bayern started. In reality, he wasn't literally involved in the tie, having departed Barca the previous summer. But Guardiola had already been announced as Jupp Heynckes' successor, and therefore the fixture was "Guardiola past" versus "Guardiola future." "Guardiola present," midway through his sabbatical in New York, remained tight-lipped.