Robben and Ribery this season agreed new deals to keep them at the club until June 2018, but Bayern are slowly preparing for life after the illustrious duo, both now in their thirties.
Douglas Costa and Kingsley Coman are expected to become Bayern's first choice wingers in the long term, but Hitzfeld feels the more experienced pair remain in a league of their own.
"Bayern are already preparing for the future, but Robben and Ribery are guaranteed starters when they are fit," Hitzfeld told TZ.
"You cannot replace players like them from one day to the other. They are not only top players, but are also on another level.
"So the strategy should be to slowly build up the players behind them. Players like Douglas Costa and Kingsley Coman are already playing regularly. They will have to step it up a notch.
"They were brought in to grow at Bayern. But you cannot expect them to just be at the same level as Robben and Ribery right away.
"Both are world-class attackers. They always have a solution on the pitch and their desire to keep going is impressive.
"Talent alone is not enough to become a world-class player. Bayern should be proud to have them on their books."