The two Dortmund professionals will start with individual running sessions before linking up with the amateurs. The same applies to the rest of the goalkeeping group, along with much of the coaching staff, physiotherapists and many other staff members.
Beier was not called up by Germany head coach Jürgen Klopp for the Nations League internationals, while Sabitzer withdrew from the Austrian national team's matches of his own accord. He said the reason for this was that he had to "manage his energy carefully".
Elsewhere, all of BVB's other fit outfield players are away with their respective national teams. A total of 20 Dortmund professionals have been nominated for the XXL international break.
As for the injured stars such as Emre Can and Justin Lerma, they will continue working on their comeback as normal in rehabilitation.