He is the sixth Dortmund midfielder to be out injured, along with Marco Reus, Ilkay Guendogan, Oliver Kirch, Nuri Sahin and Jakub Blaszczykowski.
The Armenian international, who is the driving force in Dortmund's attacking game, was injured while attempting a shot and colliding with an opponent in the 90th minute at Mainz.
"It is foreseen that he will not be able to play before the end of October." the club in a statement.
Dortmund kicked off their Champions League campaign with a win over Arsenal in midweek and Mkhitaryan will miss their next two group games against Anderlecht and Galatasaray in October.
(Reporting by Karolos Grohmann, editing by Alan Baldwin)
Share
