Mandzukic's name was surprisingly absent from the teamsheet when Bayern faced Borussia Monchengladbach last Friday night.
Instead, Mario Gotze played in attack, opening the scoring in a 2-0 win, while Mandzukic was left behind in Munich.
With Robert Lewandowski arriving from Borussia Dortmund in the summer, the Croatian may find his opportunities limited even further next season, but Kahn believes that is the normal destiny of a Bayern Munich striker.
"Just look in the past and you'll see that Bayern strikers often only have a short shelf-life," he told the Bild newspaper.
"Even when they score lots of goals, they get swapped, and Mario Mandzukic risks the same fate.
"Everybody at Bayern is dispensable, particularly the strikers."
Mandzukic has been linked with a move away from Bayern this winter, with Italian side Juventus reportedly monitoring events across the Alps.