Morris has been struggling with back injury and it is hoped that he would be able for the limited-overs fixture against Bangladesh beginning October 15 which includes three ODIs and two T20Is.
The 30-year-old has played just four Tests for the Proteas so far, in which he has taken 12 wickets at 38.25.
Steyn has been out of action since he got his right shoulder fractured during Australia's first innings of the opening Test against South Africa, which the Proteas went on to win by massive 177 runs at the WACA Ground in Perth.
The two-Test series begins in Potchefstroom on September 28 while the second match starts on October 6 in Bloemfontein. (ANI)