The Pakistan Cricket Board (PCB) confirmed this in a statement on Saturday.
Shadab was diagnosed with “high-grade full thickness tear to the Rectus Femoris muscle”, an injury he had sustained during his side’s four wickets victory over New Zealand in the Napier T20I earlier this week.
Sharing details PCB's Dr Sohail Saleem said: “The MRI reports have confirmed it is a fresh injury and not the one that had sidelined him from the Zimbabwe series last month.
“The latest injury will be treated conservatively and Shadab will undergo a six-week rehabilitation programme during which he will have weekly ultrasound scans. After the competition of the six-week period, the medical panel will access and evaluate the injury before making a call on Shadab’s return to competitive cricket.”
The Christchurch Test will be played from 3-7 January, while the two-Test and three T20I series between Pakistan and South Africa will be played from 26 January to 14 February.
Shadab will remain with the side in New Zealand, where he has started his rehabilitation programme under the supervision of the medical team.