Bavuma sustained the injury while batting in the third and final ODI of the series on Wednesday, immediately putting his availability in doubt.
The already depleted South Africa side, with Quinton de Kock, David Miller, Kagiso Rabada, Anrich Nortje, and Lungi Ngidi leaving for the IPL, will also be missing Reeza Hendricks, who withdrew from the squad, following the birth of his first-born child.
Rassie van der Dussen, who is also struggling with a grade one left quadriceps muscle strain, is likely to also miss the series opener.
Meanwhile, Dwaine Pretorius will continue to recover from his rib fracture and hasn’t been cleared yet for the series.
Aiden Markram, Andile Phehlukwyo, Daryn Dupavillon, and Wiann Mulder have been retained from the ODI squad for the upcoming matches.
The first T20I will be played on Saturday, April 10 in Johannesburg.
Full squad: Heinrich Klaasen (c), Daryn Dupavillon, Bjorn Fortuin, Beuran Hendricks, George Linde, Wihan Lubbe, Sisanda Magala, Janneman Malan, Aiden Markram, Wiaan Mulder, Andile Phehlukwayo, Migael Pretorius, Tabraiz Shamsi, Lutho Sipamla, Pite van Biljon, Rassie van der Dussen, Kyle Verreynne, Lizaad Williams (UNI)