BVB Dortmund CEO Hans-Joachim Watzke is hopeful Marco Reus will make his comeback this month, despite having yet to return to training after a long lay-off.
The Germany international has not featured since injuring his groin in the DFB-Pokal final defeat to FC Bayern München at the end of last season.
Reus was ruled out of Euro 2016 but was expected to be back for the start of the new Bundesliga campaign.
And Watzke told Sport1: "I'm not a doctor, but we do have a bit of a delay.
"Today is September 13 and there are 30 days in September, so that means we still have 17 days. Therefore, we still have a few days."
Reus will miss the Champions League tie against Legia Warsaw on Wednesday and will face a race to be fit for the Real Madrid clash on September 27.