Bayern's new faces begin in the dugout, with Nagelsmann ending a two-year spell with 2020/21 Bundesliga runners-up RB Leipzig to take the reins from Flick at the home of the record champions.
Flick leaves for the Germany national team job after an enormously successful stint that delivered seven trophies, including six in one year in 2020.
Nagelsmann, who led Leipzig to the final of the DFB Cup last season, has big shoes to fill, but Europe's most exciting young coach will be well armed to do so after adding to a side that already boasts the likes of record-breakers Robert Lewandowski and Thomas Müller.
It's in defence that Bayern have strengthened most considerably, with 22-year-old Frenchman Upamecano following Nagelsmann from Leipzig to Munich.
That eases the loss of perennial-winners David Alaba, Jerome Boateng and Javi Martinez who all depart this summer, while USA international Chris Richards' return from a season-long loan at Hoffenheim will feel like a new signing.
Young English left-back Omar Richards has also been recruited to give competition to Alphonso Davies in Bayern's other notable move in the market.
Meanwhile, Michael Cuisance (Marseille), Adrian Fein (PSV Eindhoven), Christian Früchtl (Nuremberg), Lukas Mai (Darmstadt and Joshua Zirkzee (Parma) are all back from loans away from the club and Douglas Costa heads off to Juventus following a temporary second spell in Bavaria that ended in one goal in 11 league appearances for the Brazilian.
Likewise, Tiago Dantas has been returned to Benfica and Germany U20 international Angelo Stiller will play his football at Hoffenheim next season after making his professional debut in the UEFA Champions League last term.