When Schlieffen retired in 1906, Mackensen was considered as a possible successor, but the job went to Helmuth von Moltke the Younger.
Kui Schlieffen jäi 1906 pensionile, pidasid mõned Mackenseni tema võimalikuks järglaseks, kuid selle koha sai hoopis Helmuth von Moltke Noorem.