The Germany international, who had only just returned from a lengthy spell on the sidelines, took a knock to his right foot in a friendly against Fortuna Dusseldorf
The centre-half had only made his return from the ankle problem he sustained while on international duty with Germany in November in Friday's Bundesliga win over Eintracht Frankfurt.
However, Hummels injured his right foot in a friendly game against Fortuna Dusseldorf on Tuesday evening and will be unavailable for a fortnight.
Consequently, the 25-year-old will sit out die Schwarzgelben's upcoming Bundesliga meetings with Werder Bremen and Eintracht Frankfurt, as well as the DFB-Pokal clash with the latter.
The one positive for Dortmund, though, is that scans revealed that Hummels has made a complete recovery from the ankle knock he suffered last November.